docs(adr): triage, rewrite, and renumber ADRs for clean slate

Complete ADR refactoring for issue #15:

## Changes

1. **Triage archival** — deleted chunk-era ADRs (0001–0003, 0006–0011, 0013); kept active decisions (0004, 0005, 0012, 0014+)
2. **ADR-0004 rewrite** — now reflects plugin-based skill distribution (`plugins/<name>/skills/` + `claude plugin install`) instead of monolithic `.agents/skills/` deployment
3. **Renumber to 0001–0009** — sequential clean slate after archival; all cross-references updated
4. **Content audit** — verified all 9 remaining ADRs for alignment with plugin model, removed stale chunk/deployment language

Kept ADRs: 0001–0009
- 0001: Skills distributed via plugins
- 0002: Two-tier CLAUDE.md (always-on + on-demand)
- 0003: AGENTS.md as provider-agnostic entry point
- 0004: INFO finding level in skill-audit
- 0005: agent-author dual provider scaffold
- 0006: Plugin version parity (version in both manifests)
- 0007: Gitea as exclusive issue tracker
- 0008: agent-audit single-file invocation
- 0009: agent-audit field inventory reference

All decisions are active and aligned with current repository state (marketplace/plugin model).

Closes #15 (ADR section of acceptance criteria)
Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

docs/adr/0005-agent-author-dual-provider-scaffold.md

@@ -0,0 +1,41 @@
+# agent-author generates both provider files from a single root input
+
+`agent-author` is the skill that creates Claude Code and GitHub Copilot CLI agent
+definition files. Both providers are always targeted: Claude Code produces a `.md`
+file; Copilot CLI produces a `.agent.md` file. The scaffold script `new-agent.sh`
+accepts a single root directory and derives both destination paths by convention
+rather than requiring the caller to supply two explicit paths. Scope is detected
+from the root: a directory containing `plugin.json` is plugin scope (both files
+land in `<root>/agents/`); a directory with `.git` but no `plugin.json` is project
+scope (`.claude/agents/<name>.md` + `.github/agents/<name>.agent.md`); `~` is user
+scope (`~/.claude/agents/<name>.md` + `~/.copilot/agents/<name>.agent.md`).
+
+## Considered options
+
+**Two explicit destination paths (rejected)** — `new-agent.sh <name> <claude-dest>
+<copilot-dest>` accepts a separate path per provider. Rejected because it breaks
+the minimal-input principle that guides the entire skill: the caller must now know
+and supply two provider-specific paths, which is exactly the convention knowledge
+the script is meant to encapsulate. Every invocation becomes more error-prone and
+harder to drive from a skill body without user interaction.
+
+**Plugin-only dual generation (rejected)** — generate both files only at plugin
+scope; at project/user scope generate a single file with the provider inferred from
+the destination path. Rejected because it is an artificial asymmetry: the reason to
+author for both providers does not disappear outside a plugin context. It would
+force users to run the skill twice per agent at project/user scope or build a
+separate single-provider skill, adding complexity with no benefit.
+
+## Consequences
+
+- `.github/agents/` is the locked-in Copilot CLI convention at project scope.
+  Non-standard paths (e.g. `.copilot/agents/`) are not supported without an
+  explicit override flag — deferred to a follow-on issue.
+- The script interface `new-agent.sh <name> <root>` is a stable public contract.
+  Changing to a two-destination form is a breaking change to any caller.
+- At plugin scope, both files share a single `agents/sources.md` for provenance.
+  At project/user scope, no sources file is generated — ad-hoc authoring outside a
+  research-driven workflow has no provenance chain to record.
+- The file-by-file no-op in the script (skip existing files rather than
+  overwriting) means partial state — one provider file exists, the other does not —
+  is handled by routing in the skill body, not in the script.