refactor(skill): apply ce-code-review fixes — bump to 3.2.2, fallback tests, comparison resolver

12 fixes from the multi-agent code review on PR #400:

Version 3.2.1 -> 3.2.2 across all manifests (SKILL.md frontmatter + body
header, pyproject.toml, .claude-plugin/{plugin,marketplace}.json, sync.sh
cache path). The PR ships observable behavior changes (STEP 0 logic flip,
resolver order change, badge fallback) that should not silently appear
under the same version number — the new fallback reads SKILL.md version
directly so the badge would otherwise be misleading.

render.py::_skill_version:
- `import re` moved to module top
- _VERSION_RE extracted as a module-level compiled pattern that accepts
  double-quoted, single-quoted, and unquoted YAML version scalars
- `break` -> `continue` on corrupt manifest, so a corrupt inner manifest
  no longer shadows a valid outer one
- Wrap SKILL.md read_text() in try/except for UnicodeDecodeError to keep
  badge emission from crashing on mis-encoded SKILL.md
- Docstring clarifies precedence; inline comment marks the fallback boundary
  between the manifest walk and the SKILL.md walk

tests/test_skill_version.py (new): 7 unit tests for the fallback paths
(manifest absent, manifest corrupt, corrupt-inner + valid-outer, both
absent, SKILL.md without version, single-quoted, unquoted).

tests/test_plugin_contract.py: tombstone test asserting .codex-plugin/
stays removed (was the only CI guard against accidental reintroduction).

SKILL.md:
- STEP 0 bash echoes CLAUDE_CACHE_LATEST so the model can see the
  resolved value when deciding whether to hop
- "Both shapes ship in the wild" comment now names the two cache layouts
  (nested {cache}/{version}/skills/last30days/ vs flat {cache}/{version}/)
- Comparison-mode bash invocation gets its own inline SKILL_ROOT resolver
  (latent gap: the contract tells the model to skip Step 1 on comparison
  queries, so SKILL_ROOT was previously unset there)

CHANGELOG.md: [Unreleased] entries for the resolver rewrite and the
breaking removal of Codex native-plugin support.

All 9 reviewer personas surfaced findings; 3 cross-reviewer corroboration
clusters were promoted (import re, "both shapes" comment, missing fallback
tests). Maintainability follow-up flagged: regex now duplicated across
render.py and 2 test files; could consolidate via shared lib/skill_meta.py
helper in a future PR.

CHANGELOG.md

@@ -11,6 +11,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Rename "Digg AI 1000" to just "Digg" in user-facing output (footer line, source label, inline-quote suffix, why_relevant, container attribution). Internal references to the upstream Digg AI 1000 product remain in code comments and docstrings.
 - Bump `POSTS_PER_CLUSTER` from 3 to 5 and the render-side display limit from 2 to 3 to match the per-source enrichment caps used by Reddit, HN, YouTube, TikTok, and GitHub. The previous 3/2 caps routinely truncated cluster context (e.g. dropped a Jason Calacanis quote tweet on a `cli-printing-press` run).
+- Rewrite SKILL.md path resolution. STEP 0 narrows from a global canonical-path enforcement to a Claude-Code-marketplaces-only stale-clone guard. Step 1 SKILL_ROOT resolver walks a single precedence list (Claude plugin cache, then `~/.codex/skills/`, `~/.agents/skills/`, repo checkout, `./.skills/last30days` for `npx skills add`, CWD, Gemini). Adds SKILL.md frontmatter fallback to `render.py::_skill_version` so the badge no longer prints `v?` on installs that don't include `.claude-plugin/plugin.json`.
+
+### Removed
+
+- **BREAKING for Codex native-plugin users:** `.codex-plugin/plugin.json` and the matching SKILL_ROOT resolver branch in SKILL.md Step 1. Codex users should install via `npx skills add mvanhorn/last30days-skill` or copy the skill to `~/.codex/skills/last30days/` (which `sync.sh` already writes to in this repo).
 
 ## [3.2.0] - 2026-05-09