feat(install): add --install feynman target for Pi-runtime deployment

Adds install_feynman() that deploys personas as Feynman/Pi custom subagents
and shared skills into the Feynman runtime layout, mirroring the established
opencode pattern.

Layout:
- Personas → ~/.feynman/agent/agents/<codename>.md (Pi-spec frontmatter:
  name, description, thinking, tools, output, defaultProgress,
  inheritProjectContext, inheritSkills, systemPromptMode)
- Skills → ~/.feynman/agent/skills/<name>/ (SKILL.md + references/ +
  scripts/ + data/, plus _platform-mapping.md sibling for feynman-skills
  relative refs)

Defaults & safety:
- thinking inferred per domain (high for cybersec/intel/military/academia/
  law/history/strategy, medium otherwise)
- tools allowlist tighter for offensive (cybersec) and intel/research roles;
  Pi defaults otherwise
- Builtin agents (researcher/reviewer/writer/verifier) protected: persona
  with same codename is skipped unless --skill-force overrides
- Skill topic filter shares OPENCODE_TOPICS vocabulary; new
  --feynman-topics flag mirrors --opencode-topics
- Manifest-tracked stale cleanup never deletes builtins
- purge_skills defaults False (preserves user-installed skills)

Variants:
- --install feynman → live deploy to ~/.feynman/agent/
- --install feynman-archive → review layout to personas/{agents,skills}-
  feynman-archive/ without touching ~/.feynman/

Tested via feynman-archive: 111 persona agents + 1051 skills emitted (516
filtered out by default topic policy). Frontmatter validated against the
real ~/.feynman/agent/agents/ files of a working install.

Adds feynman to the 'all' bundle and updates CLAUDE.md install table +
.gitignore for archive directories.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitignore

@@ -8,3 +8,5 @@ __pycache__/
 /skills-archive/
 /agents-opencode-archive/
 /agents-claude-archive/
+/skills-feynman-archive/
+/agents-feynman-archive/