chore(memory): job8 C — darwin-skill reinstalled full pinned tree, detached HEAD

BDR-058 + LRN-109. Root cause of the "referenced files absent" finding:
the skills CLI's skillPath only fetches SKILL.md, never sibling
references/scripts/templates dirs. Upstream HEAD matched the already-
recorded lockfile hash exactly (no drift, no tamper) — reinstalled the
full tree at that pinned SHA, detached HEAD so nothing can silently
advance. Reinstall happened outside this repo (~/.agents); this commit
is the only repo-side record. Backup of the old single-file dir kept.

.claude/memory/decisions.md

@@ -78,6 +78,7 @@ rules:
 | BDR-055 | 2026-07-07 | job5: delete memory-commit/doc-commit `pending` verbs — v2 hook rejected (BDR-037), J4-17 closed MOOT | accepted |
 | BDR-056 | 2026-07-07 | job6: deps policy = latest gated by integration, not KEEP-PINNED by default | accepted |
 | BDR-057 | 2026-07-07 | job7: secrets by reference not by value; redact at capture, not just at rest | accepted |
+| BDR-058 | 2026-07-07 | job8: darwin-skill reinstall full pinned tree, detached HEAD (skills CLI single-file-fetch gap) | accepted |
 
 ---
 
@@ -889,3 +890,12 @@ rules:
 - **Alternatives rejected**: scrub-only (chosen as the fallback in job7's own instructions if reference-by-value support were absent) — verified Claude Code DOES support `${VAR}` expansion in `mcpServers` config (user + project scope, `env`/`command`/`args`/`url`/`headers` fields — code.claude.com/docs/en/mcp.md), so the reference form was available and preferred; global `export MAGIC_API_KEY` in `~/.bashrc` — works but broadens the secret's exposure to every subprocess of every shell session, defeating the point of the redaction hook (rejected by user in favor of the scoped wrapper).
 - **Reference**: `lib/toggle-external.sh:191-192`, `hooks/rtk-rewrite.sh`, `README.md` "Adding an MCP server that needs a secret", `.gitleaks.toml`, `lib/gitflow.sh` `_gitflow_emit_pre_commit`, `Makefile` `scan-secrets`; commits `b9300c3`/`3340c7d`/`17bdd08`/`5d5b386`. Linked to [[BDR-026]] (canonical vault this closes a leak vector against), [[LRN-108]] (the `claude mcp add --env` trap).
 - **Caveat — contradicts job6's own finding same day**: job6's journal (2026-07-07, earlier same day) states "`${VAR}` env-expansion confirmed unsupported at `~/.claude.json` user scope after 2 rounds of sourced doc lookup". job7's doc lookup (claude-code-guide agent, same day) found it IS supported at user scope, citing code.claude.com/docs/en/mcp.md + a v2.1.161 changelog entry. Not reconciled — could be a version bump between the two lookups, or job6's research being wrong. The `${MAGIC_API_KEY}` rewrite is live (`claude mcp list` recognizes the reference and reports the var missing, which requires the CLI to have at least PARSED the `${...}` syntax) but full end-to-end confirmation (restart terminal + Claude Code, verify magic MCP reconnects) is still a residual the user needs to do — see BDR-057's own commit message.
+
+## BDR-058 — job8: darwin-skill reinstall full pinned tree, detached HEAD
+
+- **Date**: 2026-07-07
+- **Status**: accepted
+- **Decision**: darwin-skill non-functional past SKILL.md text — `references/`, `scripts/`, `templates/` absent, referenced but never fetched. Root cause: `~/.agents/.skill-lock.json` `skillPath: "SKILL.md"` — installer (`skills` CLI, vercel-labs/skills) fetches ONLY that one file, not sibling dirs. Upstream repo HEAD (`7c7b7909b630dc3b5cbb91bd4bcb1b10bfb1f894`) matches lockfile hash exactly — zero drift, zero tamper, SKILL.md byte-identical old vs new. Fix: cloned upstream at that SHA, copied full tree into `~/.agents/skills/darwin-skill/`, verified all 5 referenced paths present, HEAD detached (no branch tracking, no silent advance on a stray `git pull`). Old single-file dir backed up to `~/.agents/skills/.job8-backups/darwin-skill.single-file.<ts>` first.
+- **Why**: user picked reinstall-pinned over remove/keep-broken (job8 audit §4 item 4, 3-way choice). Unverifiable skill can't be trusted; user wants the optimizer kept, not removed.
+- **Alternatives rejected**: remove entry (kills wanted function); keep as-is (fails job8's own audit bar — unverifiable); flat-copy without `.git` (matches other 34 dormant skills' convention but drops verifiable pin — kept `.git` detached instead, darwin-skill now 2nd real SHA-pin in the whole trust chain after gstack, job8 report §5).
+- **Reference**: `~/.agents/skills/darwin-skill/` (detached HEAD `7c7b790`), `~/.agents/.skill-lock.json` (untouched, hash still accurate), backup at `~/.agents/skills/.job8-backups/`. Outside this repo — no commit here covers the file placement itself, this entry is the record. Git-commit whole-`.claude/skills`-tree scope (job8 C.2, `SKILL.md:115/201`) NOT restricted — 3rd-party pinned code, patching it breaks the pin; accepted as documented risk, human-checkpoint-gated per job8 report. Linked to [[LRN-109]].