chore(skill): Own tttk-authoring in the repo

Move the skill to .agents/skills/tttk-authoring and point gen:skill-reference at it. Activate it by symlinking ~/.agents/skills/tttk-authoring to the in-repo copy.

Extend the reference drift guard to cover the skill copy now that it is versioned, and document activation in docs/development.md.

.agents/skills/tttk-authoring/examples/adventure.md

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+# The Hollow Mill
+
+## Adventure brief
+
+The mill on the village edge has stood silent for a year. Last week its wheel
+began turning again — on its own.
+
+> [!WARNING]
+> The mill's guardian is not hostile by default. Attacking it forfeits the
+> peaceful resolution.
+
+## Locations
+
+:md-table[./locations.csv]
+
+## Random encounters
+
+:md-table[./encounters.csv]{roll=true}
+
+## The mill guardian
+
+:md-dice[1d20+3]{key="guardian-attack"}
+
+The guardian strikes with :[sword] for :md-dice[2d6+2]{key="guardian-damage"}.
+
+## Encounter table (inline)
+
+```csv role=spark-table roll=true
+d6,Encounter
+1,A crow watches from the rafters.
+2,The floorboards groan underfoot.
+3,A cold draft carries the smell of grain.
+4,The wheel outside stops for one breath.
+5,A sack of flour splits open.
+6,The guardian's lantern flickers to life.
+```
+
+## Route
+
+```mermaid
+graph TD
+    A[Village] --> B[Mill Road]
+    B --> C{Mill Door}
+    C -->|Force| D[Ground Floor]
+    C -->|Listen| E[Secret Cellar]
+    D --> F[Wheel Room]
+    E --> F
+```
+
+## Guardian card
+
+```yaml role=tag
+tag: md-deck
+body: ./guardian.csv
+data-config:
+  size: 63x88
+  grid: 5x5
+  layers:
+    - prop: name
+      pos: 1,1-5,1
+      font: 12
+    - template: |
+        **{{type}}** — {{hp}} HP
+        {{description}}
+      pos: 1,3-5,8
+      font: 3
+      align: l
+```

.agents/skills/tttk-authoring/examples/encounters.csv

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+group,label,body
+Mill Road,1,"### A crow on the fence
+
+A crow fixes you with one eye, then flies toward the mill.
+
+**Interaction**: Follow it (Perception 3/1)
+
+**Risk**: None"
+Mill Road,2,"### Broken cart
+
+An overturned cart blocks half the road.
+
+**Interaction**: Clear it (Strength 3/2)
+
+**Risk**: Failure costs 1 Stamina"
+Mill Road,3,"### Cold spot
+
+The air turns suddenly cold.
+
+**Interaction**: Press on (Constitution 3/1)
+
+**Risk**: Failure deals 1 Constitution damage"
+Wheel Room,1,"### The turning wheel
+
+The wheel grinds without water.
+
+**Interaction**: Jam the gears (Strength 3/3)
+
+**Risk**: Failure deals 1 Agility damage"
+Wheel Room,2,"### Flour dust
+
+Thick dust fills the air.
+
+**Interaction**: Cover your mouth (Constitution 3/1)
+
+**Risk**: Failure deals 1 Constitution damage"

.agents/skills/tttk-authoring/examples/guardian.csv

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+label,name,type,hp,description
+1,The Hollow Miller,Spirit,10,"Bound to the wheel by an old promise. Speaks only in the sound of grinding stone."

.agents/skills/tttk-authoring/examples/locations.csv

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+label,body
+Village,"### Village
+
+**Type**: Starting location
+
+A quiet village at the edge of the marsh. The miller's daughter asks after her
+father.
+
+**Interaction**: Ask about the mill (Charisma 3/1)
+
+**Supplies**: Rope, torches, one healing draught"
+Mill Road,"### Mill Road
+
+**Type**: Route
+
+A muddy track winding between hedgerows toward the mill.
+
+**Interaction**: Spot tracks (Perception 3/1)
+
+**Encounters**: 3 random encounters"
+Ground Floor,"### Ground Floor
+
+**Type**: Hub
+
+Sacks of grain, a cold hearth, and a ladder to the wheel room.
+
+**Interaction**:
+- Search the hearth (Perception 3/2) — find a brass key
+- Climb the ladder (Agility 3/1)"
+Secret Cellar,"### Secret Cellar
+
+**Type**: Archive
+
+A low cellar beneath the millstones. Ledgers line the walls.
+
+**Interaction**: Read the ledgers (Intelligence 3/2) — learn the guardian's name
+
+**Clue**: The last entry is dated one year ago, in the miller's hand"
+Wheel Room,"### Wheel Room
+
+**Type**: Finale
+
+The great wheel turns in silence, though no water reaches it.
+
+**Interaction**:
+- Speak the guardian's name (Charisma 3/3) — peaceful resolution
+- Break the wheel (Strength 3/4) — hostile resolution"