refactor(gitea-workflow): retrofit to the ADR-0020 context contract

Description 1012 -> 347 chars, body 582 -> 170 words, Gotchas 3 entries -> 1 at
22.9% of body. Clears the description FAIL and all four Vale CompositionNote
errors -- the last carriers in the corpus, so that rule now fires nowhere.

Cut the 'human-facing entry point and router' architecture note, the /gitea
migration history and the six-skill composition list; all were already in the
README or the routing table.

Split three mutually exclusive flows into a dispatch table keyed on invocation
shape, each branch self-contained in references/: status-checkin.md,
number-resolution.md, skill-index.md. Report stays in the body as the gate
common to every branch; each branch's own format moved to its file. The old
Step 1-4 numbering presented three alternatives as a sequence.

The description grew from an intermediate 283 chars on purpose: that draft had
dropped flow 3's trigger entirely, leaving the domain-routing index -- a third
of the skill -- reachable only through a tail clause whose grammatical subject
was the request rather than the skill. Both gates were green over that.

Boundary clauses are one arrow per target, so both resolve (#107: the resolver
extracts only the first target per clause and reports 1 of 1 on a clause naming
two). The local-git exclusion keeps its wording but drops the route to
git-workflow, which would not resolve in a gitea-only install.

Known residual: the dispatch conditions are stated twice, as a table and as
literal conditionals. That is #109 -- body-discipline.md mandates the literal
form while the ADR's cited exemplar, apm-workflow, uses a bare table plus one
summary line. Fixing it here would settle that contradiction in a skill rather
than in the spec, so it rides with #109.

Refs #99, #107, #109

plugins/gitea/.apm/skills/gitea-workflow/references/sources.md

@@ -3,9 +3,9 @@
 ## gitea-mcp-repo
 
 - **URL:** https://gitea.com/gitea/gitea-mcp
-- **Description:** Official gitea-mcp repository (v1.3.0) — `operation/*.go` source files documenting all 55 MCP tools. This skill's status view relies on `list_issues`/`list_pull_requests` semantics (via `gitea-issues`/`gitea-prs`), and its ambiguous-number resolution relies on `issue_read`'s `is_pull` field, both verified against this source at authoring time.
+- **Description:** Official gitea-mcp repository (v1.3.0) — `operation/*.go` source files documenting all 55 MCP tools. This skill's status view relies on `list_issues`/`list_pull_requests` semantics (via `gitea-issues`/`gitea-prs`), its ambiguous-number resolution relies on `issue_read`'s `is_pull` field, and its domain-skill index groups that tool surface by owning skill — all verified against this source at authoring time.
 - **Research doc:** plugins/gitea/docs/research/docs/gitea/sources.md
-- **Contributing files:** SKILL.md
+- **Contributing files:** references/status-checkin.md, references/number-resolution.md, references/skill-index.md
 - **Status:** `extracted`
 
 ## gitea-mcp-slim-go
@@ -13,7 +13,7 @@
 - **URL:** https://gitea.com/gitea/gitea-mcp/raw/branch/main/operation/issue/slim.go
 - **Description:** Slim response shape structs from gitea-mcp source — confirms `is_pull` is present on a single-item `issue_read` response, the field this skill's resolution step depends on to distinguish an issue from a PR sharing the same number.
 - **Research doc:** plugins/gitea/docs/research/docs/gitea/sources.md
-- **Contributing files:** SKILL.md
+- **Contributing files:** references/number-resolution.md
 - **Status:** `extracted`
 
 ## context7-websites-gitea
@@ -21,7 +21,7 @@
 - **URL:** context7:/websites/gitea
 - **Description:** Official Gitea docs mirror on Context7 — confirms issues and pull requests share a single per-repository number sequence, and that Gitea returns 404 for permission failures rather than a distinct 403, both facts this skill's resolution and error-handling steps depend on.
 - **Research doc:** plugins/gitea/docs/research/docs/gitea/sources.md
-- **Contributing files:** SKILL.md
+- **Contributing files:** references/number-resolution.md
 - **Status:** `extracted`
 
 ## context7-gitea-tea-cli