M6.5: StepSkills + ability-bonus breakdown + Aside redesign

The skills step lands as the last data-driven character creation step
(only Sign — name + confirm — remains for M6.6). Brought a few cross-
cutting refactors with it.

Scenes/Steps/StepSkills.cs:
  Direct port of StepSkills in src/steps.jsx — all 18 skills laid out
  in 6 ability-grouped panels (STR/DEX/CON/INT/WIS/CHA), 2-column
  grid. Background-granted skills appear pre-checked and locked;
  user picks `class.SkillsChoose` more from `class.SkillOptions`.
  Hover the skill name → popover with the codex flavor description
  (limited to the title only — hovering checkboxes / source tags
  doesn't trigger the popover, avoids interference with adjacent
  rows' click targets). Fixed-width [✓] / [ ] / [—] checkbox slot
  so toggling doesn't shift the row layout.

UI/SkillsCatalog.cs (new):
  Static skill table — JSON id, display label, governing ability,
  and the codex SKILL_DESC text ported verbatim from src/data.jsx.
  Mirrors Theriapolis.Core.Rules.Stats.SkillId; descriptions live
  here because backgrounds.json and classes.json don't carry them.

UI/AbilityCalc.cs (new):
  Final-score math — base assignment + clade and species mods, with
  per-source breakdown for the bonus popover ("+1 from Canidae · +2
  from Wolf"). Hybrid mode tags each clade source with its lineage
  ("(sire)" / "(dam)"). Used by both StepStats and the Aside so the
  two views can never disagree on what a +N badge means.

UI/BackgroundAvailability.cs (new):
  Extracted from StepBackground — shared rules table for hybrid-only
  and clade-restricted backgrounds. Now also consulted by StepClade
  when the player changes lineage: the currently-selected background
  is auto-cleared if the new lineage no longer satisfies its rule
  (e.g., Pack-Raised clears when switching from Canidae to Felidae,
  Passer clears when toggling Hybrid off). Implemented via
  Resource.Duplicate + Patch on the duplicate to evaluate the
  hypothetical post-patch state without committing prematurely.

StepStats.cs:
  Per-row layout extended: ability label | slot | bonus chip | final
  | d20 mod. Bonus chip is a TraitChip with the per-source breakdown
  in its hover description. Auto-assign now sorts empty abilities by
  AbilityCalc.TotalBonus DESCENDING (with class.PrimaryAbility as
  tiebreaker) — biggest pool value lands on the ability already
  receiving the biggest lineage bonus, maximising final scores.

Aside.cs (significant redesign):
  - Name centered at top.
  - Lineage details: 2-column grid, full-width.
    - Purebred:  Clade | Species, then Calling | Background, then
                 Subclass | (empty).
    - Hybrid:    SIRE ★ | DAM (centered + underlined column heads),
                 Clade | Clade, Species | Species, then the same
                 calling/background/subclass rows.
  - Attributes: STR/DEX/CON/INT/WIS/CHA each with bonus chip (omitted
    when +0), final score, d20 modifier. Self-contained min-width
    table so it can't widen the panel beyond its alloc.
  - Pills: traits, detriments, level-1 features, background feature,
    skill chips (BG-locked + user-chosen). All hoverable for descriptions.
  - Whole panel wraps in a ScrollContainer so an over-tall summary
    scrolls in place instead of pushing the wizard layout off-screen.
  - Width nudged 320 → 360px. Smaller font on label tags, autowrap
    on value labels so long names ("Hybrid Underground") wrap rather
    than push the panel wider.

Card grids: changed all five card-grid steps (Clade, Species, Class,
Subclass, Background) from SizeFlagsHorizontal.ExpandFill →
ShrinkCenter. Cards stay at their CustomMinimumSize 200 wide and
the grid horizontally centers in PageMain. The right-side gap
between content and Aside is now uniform regardless of how many
cards or whether the last row is partial — fixes the "Clade tab
feels too padded, Background tab too tight" perception.

Closes M6.5. Per guide §12, what's left in M6: M6.6 (StepReview —
name + summary + Confirm handoff per guide §11) and M6.7 (parchment
Theme pass).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Theriapolis.Godot/UI/SkillsCatalog.cs

@@ -0,0 +1,78 @@
+namespace Theriapolis.GodotHost.UI;
+
+/// <summary>
+/// All 18 skills with display labels, governing ability, and codex
+/// flavor descriptions. Entries are keyed by their snake_case JSON id —
+/// the same string that appears in <c>class.skill_options</c> and
+/// <c>background.skill_proficiencies</c> in <c>Content/Data</c>.
+///
+/// Labels and ability mapping mirror Theriapolis.Core.Rules.Stats.SkillId;
+/// descriptions are ported verbatim from <c>src/data.jsx</c>'s
+/// <c>SKILL_DESC</c> table in the React prototype. If the JSON schema
+/// gains a description field later, swap to a data-driven lookup.
+/// </summary>
+public static class SkillsCatalog
+{
+    public record SkillEntry(string JsonId, string Label, string Ability, string Description);
+
+    public static readonly SkillEntry[] All =
+    {
+        new("acrobatics",      "Acrobatics",       "DEX",
+            "Tumbling, balance, and the kind of footwork that keeps you upright on a coliseum sand-floor or a warren-rope. Body-cunning under pressure."),
+        new("animal_handling", "Animal Handling",  "WIS",
+            "Reading and steering non-sentient beasts — feral hounds, draft-kine, the wild cousins of your own clade. Calming, herding, riding."),
+        new("arcana",          "Arcana",           "INT",
+            "Knowledge of the older magics: scent-sorcery, blood-sigil, the half-forgotten rites that pre-date the Covenant of Claws."),
+        new("athletics",       "Athletics",        "STR",
+            "Raw physical effort. Climbing scaffold, swimming the foul canal, hauling a packmate from the pit, breaking a hold."),
+        new("deception",       "Deception",        "CHA",
+            "Speaking convincingly past your scent. The art of the false posture, the planted rumor, the answer that is technically true."),
+        new("history",         "History",          "INT",
+            "The long memory of Theriapolis — the Imperium's fall, the Compact's ratification, which clade owes which other a centuries-old debt."),
+        new("insight",         "Insight",          "WIS",
+            "Reading another's true posture beneath their words. Catching the off-note in a snarl, the held breath, the lie in a friendly tail."),
+        new("intimidation",    "Intimidation",     "CHA",
+            "Bared-teeth diplomacy. The threat made plain enough that violence is not required to extract compliance."),
+        new("investigation",   "Investigation",    "INT",
+            "Methodical search and inference: scene-reading, document-sifting, the patient accumulation of small facts into a verdict."),
+        new("medicine",        "Medicine",         "WIS",
+            "Field surgery, poultice-craft, knowing which clade tolerates which tincture. Stabilizing the dying without finishing them."),
+        new("nature",          "Nature",           "INT",
+            "Knowledge of the wild outside the city wall — terrain, weather, plant-lore, and the unsigned beasts that observe no Covenant."),
+        new("perception",      "Perception",       "WIS",
+            "Awareness through every sense your clade gives you: ear-cock, scent-prickle, the half-glimpsed shape at the edge of vision."),
+        new("performance",     "Performance",      "CHA",
+            "Holding an audience — coliseum crowd, courtroom gallery, market square. Song, oratory, the body that compels watching."),
+        new("persuasion",      "Persuasion",       "CHA",
+            "Open-handed argument. The case made on its merits, the appeal to mutual benefit, the patient construction of agreement."),
+        new("religion",        "Religion",         "INT",
+            "The hymn-cycles of the Cervid liturgy, the Compact's sacred clauses, the small household rites your clade keeps without thinking."),
+        new("sleight_of_hand", "Sleight of Hand",  "DEX",
+            "Quiet fingers — pickpocketing, palmed coins, the swap performed under another's nose. Useful in markets and courtrooms alike."),
+        new("stealth",         "Stealth",          "DEX",
+            "Movement unseen and unsmelled. Wind-checking, scent-suppression, the slow weight-shift on a creaking floor."),
+        new("survival",        "Survival",         "WIS",
+            "Field-craft beyond the wall: tracking, foraging, fire-making, knowing which run-off is safe to drink and which carries the upstream butcher's leavings."),
+    };
+
+    public static readonly string[] Abilities = { "STR", "DEX", "CON", "INT", "WIS", "CHA" };
+
+    public static readonly System.Collections.Generic.Dictionary<string, string> AbilityFullName = new()
+    {
+        { "STR", "Strength"     },
+        { "DEX", "Dexterity"    },
+        { "CON", "Constitution" },
+        { "INT", "Intellect"    },
+        { "WIS", "Wisdom"       },
+        { "CHA", "Charisma"     },
+    };
+
+    public static SkillEntry? Get(string jsonId) =>
+        System.Array.Find(All, s => s.JsonId == jsonId);
+
+    public static System.Collections.Generic.IEnumerable<SkillEntry> ByAbility(string ability)
+    {
+        foreach (var s in All)
+            if (s.Ability == ability) yield return s;
+    }
+}