feat: implement issue 0018 phase 1 — factory/write-skill bootstrap skill

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.agents/evals/factory/write-skill/eval.yaml

@@ -0,0 +1,68 @@
+skill_name: write-skill
+
+trigger_tests:
+  - id: explicit-trigger-new-skill
+    name: Explicit — new skill phrase
+    query: "Write a new skill for handling database migrations"
+    should_trigger: true
+
+  - id: implicit-trigger-no-phrase
+    name: Implicit — no trigger phrase
+    query: "I want to add a skill that automates our deploy process"
+    should_trigger: true
+
+  - id: implicit-trigger-conversion
+    name: Implicit — placeholder conversion
+    query: "The grill-me skill is a Pocock placeholder, can you convert it to our standard?"
+    should_trigger: true
+
+  - id: negative-trigger-upgrade
+    name: Negative — existing skill fix
+    query: "The tdd skill is producing wrong output, fix it"
+    should_trigger: false
+
+  - id: negative-trigger-code-refactor
+    name: Negative — code refactor
+    query: "Refactor this module to use the new API client"
+    should_trigger: false
+
+  - id: negative-trigger-write-eval
+    name: Negative — eval request
+    query: "Write evals for the diagnose skill"
+    should_trigger: false
+
+output_tests:
+  - id: output-has-all-sections
+    name: All 8 body sections present
+    type: deterministic
+    prompt: "Write a new skill for linting markdown files, category: implement"
+    expected_output: A complete SKILL.md containing all 8 required body sections in order.
+    assertions:
+      - "Output contains '## Role'"
+      - "Output contains '## When to use / When not to use'"
+      - "Output contains '## Required inputs'"
+      - "Output contains '## Constraints'"
+      - "Output contains '## Process'"
+      - "Output contains '## Output format'"
+      - "Output contains '## Failure handling'"
+      - "Output contains '## Self-check'"
+
+  - id: output-path-correct
+    name: Output path and frontmatter fields correct
+    type: deterministic
+    prompt: "Write a new skill for linting markdown files, category: implement"
+    expected_output: A SKILL.md with correct output path stated and all required frontmatter fields present.
+    assertions:
+      - "Output contains '.agents/skills/' in the stated output path"
+      - "Output contains 'metadata:' and 'category:' in frontmatter"
+      - "Output contains 'version:'"
+      - "Output contains 'when:'"
+
+  - id: output-trigger-tested-before-body
+    name: Trigger description tested before body content written
+    type: llm-rubric
+    prompt: "Write a new skill for summarising pull request diffs"
+    expected_output: The skill presents a trigger description and tests it against at least 3 cases (explicit, implicit, negative) before proposing or writing any body section content.
+    assertions:
+      - "The skill proposes a trigger description and explicitly tests it against an explicit query, an implicit query, and a negative query before writing any body section"
+      - "The skill walks through each body section individually and seeks confirmation before writing the file"