feat(boss): file skill-system deficiencies to the plugin's own tracker

Under /boss only, when the orchestrator hits a durable deficiency in the
plugin itself (a skill, agent, convention, or pipeline/cascade gap)
mid-run, it files an issue against the plugin's own tracker and continues,
marking provenance with a body block — no new label, so the fixed work-type
vocabulary stays intact.

Adds the trigger and its evidence gate (a citable path:line inside the
plugin), dedupe-as-gate over open and recently-closed issues, and the
discipline that filing is neither a notify event nor a substitute for a due
bounce-back. Wires the new section into issue/SKILL.md (boss joins the
issue-filing callers) and docs/conventions.md (Issue-tracker pointer).

closes #9

issue/SKILL.md

@@ -30,7 +30,10 @@ is not a chat message.
 
 Other skills file issues through these same conventions — e.g.
 `brainstorm` parks a deferred spec as a backlog issue, `audit` files
-regressions. This skill is the shared convention they lean on.
+regressions, and `boss` files skill-system deficiencies against the
+plugin's own tracker (with an autonomous-provenance body block — see
+`../boss/SKILL.md` § Skill-system feedback). This skill is the shared
+convention they lean on.
 
 ## The four writing rules
 
@@ -145,5 +148,7 @@ Notes:
 
 - `~/dev/CLAUDE.md` — repo-English rule, label vocabulary, the
   `closes #N` commit convention (the tracker is the forward-queue).
-- `../brainstorm/SKILL.md`, `../audit/SKILL.md` — callers that file
-  issues through these conventions.
+- `../brainstorm/SKILL.md`, `../audit/SKILL.md`, `../boss/SKILL.md` —
+  callers that file issues through these conventions (`boss` files
+  skill-system feedback on the plugin's own tracker with an
+  autonomous-provenance body block, § Skill-system feedback).