docs(agent): vendor-neutral agent docs — AGENTS.md entry, agent/ SoT, .claude shims

The repo is maintained by agents from multiple vendors, so agent
instructions move out of vendor-specific locations into shared,
git-tracked markdown:

- AGENTS.md is the new entry point for any harness; CLAUDE.md becomes a
  symlink to it (Claude Code keeps working unchanged).
- Skill bodies relocate to agent/: VERIFICATION.md (the enforcement
  rules, ex .claude/skills/nomarchy), DELEGATION.md (capability tiers
  light/standard/frontier, scout/runner role contracts, token economy,
  parallel fan-out — consolidates the CLAUDE.md model table, LOOP.md's
  economy section, and skill §6.5 into one place; vendor model names
  survive only in the per-harness mapping table), THEME-DESIGN.md
  (ex .claude/skills/theme, which previously lacked frontmatter).
- .claude/ shrinks to a thin Claude Code adapter: settings, subagent
  defs, and skill shims that route into agent/.
- Maps updated: agent/README.md (instructions vs state vs adapters),
  docs/README.md, README.md layout tree.

Cleanup: stale old_distro .gitignore entry dropped (dir long gone);
local result*/__pycache__ artifacts removed; JOURNAL.md rotated (29
recent entries kept, 120 older moved to agent/JOURNAL-ARCHIVE.md,
rotation rule documented in the header).

Verification: V0 (docs/meta only) — nix flake check --no-build exit 0
with the tracked symlink; grep sweep confirms no vendor model names
outside DELEGATION.md's mapping table.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

agent/MEMORY.md

@@ -162,8 +162,9 @@ iteration would otherwise rediscover.
   effects carry a value, matchers take `match:` (§ windowrule migration).
 - grub `loadfont`s every `.pf2` in a theme dir — reuse a bundled DejaVu
   rather than shipping fonts (§ Distro branding).
-- `.claude/skills/*/SKILL.md` are now **tracked** (the `.gitignore`
-  `.claude/skills/` line was un-commented→removed, 7d52d4b) — commit skill
-  edits like any repo doc. Still never `git add -A` blindly: check
-  `git status --short` for genuine strangers first (`settings.local.json`,
-  harness-dropped files) and commit with explicit pathspecs (§ loop hygiene).
+- `.claude/skills/*/SKILL.md` are **tracked thin shims** — the actual
+  instruction bodies live vendor-neutrally in `agent/` (VERIFICATION,
+  DELEGATION, THEME-DESIGN); edit those, not the shims. Still never
+  `git add -A` blindly: check `git status --short` for genuine strangers
+  first (`settings.local.json`, harness-dropped files) and commit with
+  explicit pathspecs (§ loop hygiene).