feat: add Codex agents/openai.yaml metadata to every skill

Adds an `agents/openai.yaml` beside each `SKILL.md` so the skills work in
Codex as well as Claude Code, without generated copies:

- `interface.display_name` + `interface.short_description` for the Codex
  skill picker, hand-written for all 39 skills.
- `policy.allow_implicit_invocation: false` on the 22 user-invoked skills —
  the Codex analog of `disable-model-invocation: true`, so Codex excludes
  them from implicit invocation while explicit `$skill` still works.
- Document the dual-harness invocation model in `.agents/invocation.md`,
  `CLAUDE.md`, and the promoted-bucket READMEs.
- Add `AGENTS.md` as a symlink to `CLAUDE.md` so Codex reads the same
  instructions; note Codex as a `link-skills.sh` install target.

Slimmed-down rework of the approach prototyped in #522: keeps the essential
cross-harness metadata, drops the Ruby validator, the runtime-detector test,
per-skill `default_prompt`s, and the unrelated promotion changes.

Co-authored-by: gabimoncha <gabimoncha@users.noreply.github.com>
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

skills/engineering/README.md

@@ -4,7 +4,7 @@ Skills I use daily for code work.
 
 ## User-invoked
 
-Reachable only when you type them (`disable-model-invocation: true`).
+Reachable only when you type them (Claude Code: `disable-model-invocation: true`; Codex: `policy.allow_implicit_invocation: false` in `agents/openai.yaml`).
 
 - **[ask-matt](./ask-matt/SKILL.md)** — Ask which skill or flow fits your situation. A router over the user-invoked skills in this repo.
 - **[grill-with-docs](./grill-with-docs/SKILL.md)** — Grilling session that also builds your project's domain model, sharpening terminology and updating `CONTEXT.md` and ADRs inline.

skills/engineering/ask-matt/agents/openai.yaml

@@ -0,0 +1,5 @@
+interface:
+  display_name: "Ask Matt"
+  short_description: "Find the right skill or workflow"
+policy:
+  allow_implicit_invocation: false

skills/engineering/code-review/agents/openai.yaml

@@ -0,0 +1,3 @@
+interface:
+  display_name: "Code Review"
+  short_description: "Review a diff on standards and spec"

skills/engineering/codebase-design/agents/openai.yaml

@@ -0,0 +1,3 @@
+interface:
+  display_name: "Codebase Design"
+  short_description: "Vocabulary for deep-module design"

skills/engineering/diagnosing-bugs/agents/openai.yaml

@@ -0,0 +1,3 @@
+interface:
+  display_name: "Diagnosing Bugs"
+  short_description: "Diagnose hard bugs and regressions"

skills/engineering/domain-modeling/agents/openai.yaml

@@ -0,0 +1,3 @@
+interface:
+  display_name: "Domain Modeling"
+  short_description: "Build and sharpen a domain model"

skills/engineering/grill-with-docs/agents/openai.yaml

@@ -0,0 +1,5 @@
+interface:
+  display_name: "Grill with Docs"
+  short_description: "Grill a design and write its docs"
+policy:
+  allow_implicit_invocation: false

skills/engineering/implement/agents/openai.yaml

@@ -0,0 +1,5 @@
+interface:
+  display_name: "Implement"
+  short_description: "Build work from a spec or tickets"
+policy:
+  allow_implicit_invocation: false

skills/engineering/improve-codebase-architecture/agents/openai.yaml

@@ -0,0 +1,5 @@
+interface:
+  display_name: "Improve Codebase Architecture"
+  short_description: "Find and grill architecture improvements"
+policy:
+  allow_implicit_invocation: false

skills/engineering/prototype/agents/openai.yaml

@@ -0,0 +1,3 @@
+interface:
+  display_name: "Prototype"
+  short_description: "Prototype to answer a design question"

skills/engineering/research/agents/openai.yaml

@@ -0,0 +1,3 @@
+interface:
+  display_name: "Research"
+  short_description: "Research from high-trust sources"

skills/engineering/resolving-merge-conflicts/agents/openai.yaml

@@ -0,0 +1,3 @@
+interface:
+  display_name: "Resolving Merge Conflicts"
+  short_description: "Resolve merge and rebase conflicts"

skills/engineering/setup-matt-pocock-skills/agents/openai.yaml

@@ -0,0 +1,5 @@
+interface:
+  display_name: "Setup Matt Pocock Skills"
+  short_description: "Configure a repo for the skills"
+policy:
+  allow_implicit_invocation: false

skills/engineering/tdd/agents/openai.yaml

@@ -0,0 +1,3 @@
+interface:
+  display_name: "TDD"
+  short_description: "Test-driven red-green-refactor"

skills/engineering/to-spec/agents/openai.yaml

@@ -0,0 +1,5 @@
+interface:
+  display_name: "To Spec"
+  short_description: "Turn a conversation into a spec"
+policy:
+  allow_implicit_invocation: false

skills/engineering/to-tickets/agents/openai.yaml

@@ -0,0 +1,5 @@
+interface:
+  display_name: "To Tickets"
+  short_description: "Split a plan into tracer-bullet tickets"
+policy:
+  allow_implicit_invocation: false

skills/engineering/triage/agents/openai.yaml

@@ -0,0 +1,5 @@
+interface:
+  display_name: "Triage"
+  short_description: "Move issues through triage roles"
+policy:
+  allow_implicit_invocation: false

skills/engineering/wayfinder/agents/openai.yaml

@@ -0,0 +1,5 @@
+interface:
+  display_name: "Wayfinder"
+  short_description: "Map a large effort as decision tickets"
+policy:
+  allow_implicit_invocation: false