t3-provision-users: vendor agent skills + per-user install_skills (emo)

Make the admin's Claude Code agent skills available to the `emo` devvm user.
Viktor asked to install Matt Pocock's skills for emo, starting with grill-me
but covering the full set the admin already uses.

The `npx skills` upstream has drifted off that set (diagnose -> diagnosing-bugs
and write-a-skill -> writing-great-skills were renamed; caveman + zoom-out are
no longer published), so reproducing it via npx is impossible and would also
spray ~70 agent dirs into the user's home + add a GitHub-clone + unpinned-CLI
dependency to the hourly root reconcile. Instead vendor a point-in-time
snapshot of the 16 skills (scripts/workstation/claude-skills/) and copy them
per-user, mirroring install_memory: install_skills() copies each skill into
~/.agents/skills/<name> (owned by the user) and symlinks
~/.claude/skills/<name> -> ../../.agents/skills/<name>. if-absent, additive,
best-effort, scoped to the SKILL_USERS allowlist (emo).

find-skills is from vercel-labs/skills (not Matt Pocock) but included since it
is part of the admin's current set.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

scripts/workstation/claude-skills/caveman/SKILL.md

@@ -0,0 +1,49 @@
+---
+name: caveman
+description: >
+  Ultra-compressed communication mode. Cuts token usage ~75% by dropping
+  filler, articles, and pleasantries while keeping full technical accuracy.
+  Use when user says "caveman mode", "talk like caveman", "use caveman",
+  "less tokens", "be brief", or invokes /caveman.
+---
+
+Respond terse like smart caveman. All technical substance stay. Only fluff die.
+
+## Persistence
+
+ACTIVE EVERY RESPONSE once triggered. No revert after many turns. No filler drift. Still active if unsure. Off only when user says "stop caveman" or "normal mode".
+
+## Rules
+
+Drop: articles (a/an/the), filler (just/really/basically/actually/simply), pleasantries (sure/certainly/of course/happy to), hedging. Fragments OK. Short synonyms (big not extensive, fix not "implement a solution for"). Abbreviate common terms (DB/auth/config/req/res/fn/impl). Strip conjunctions. Use arrows for causality (X -> Y). One word when one word enough.
+
+Technical terms stay exact. Code blocks unchanged. Errors quoted exact.
+
+Pattern: `[thing] [action] [reason]. [next step].`
+
+Not: "Sure! I'd be happy to help you with that. The issue you're experiencing is likely caused by..."
+Yes: "Bug in auth middleware. Token expiry check use `<` not `<=`. Fix:"
+
+### Examples
+
+**"Why React component re-render?"**
+
+> Inline obj prop -> new ref -> re-render. `useMemo`.
+
+**"Explain database connection pooling."**
+
+> Pool = reuse DB conn. Skip handshake -> fast under load.
+
+## Auto-Clarity Exception
+
+Drop caveman temporarily for: security warnings, irreversible action confirmations, multi-step sequences where fragment order risks misread, user asks to clarify or repeats question. Resume caveman after clear part done.
+
+Example -- destructive op:
+
+> **Warning:** This will permanently delete all rows in the `users` table and cannot be undone.
+>
+> ```sql
+> DROP TABLE users;
+> ```
+>
+> Caveman resume. Verify backup exist first.