SecurityValidator: wire installer to materialize ~/.pai/package.json + bun install + PAI/PAISECURITYSYSTEM (#158 follow-up)

[virtualian]

Background

PR #159 (closing #158) restores the shipping artefacts (Releases/v4.0.3+/.claude/package.json, Releases/v4.0.3+/.claude/PAI/PAISECURITYSYSTEM/patterns.example.yaml) so that future installs would close the SecurityValidator no-op regression — but only if the installer also has a step that materializes ~/.pai/PAI/... from the cloned ~/.claude/PAI/... and runs bun install in ~/.pai/ to populate node_modules/yaml/.

Today there is no such step. The installer's engine/steps.ts has 8 steps; none of them touch ~/.pai/PAI/ or run bun install anywhere. migratePerPackSymlinks handles skills/ only.

Required work

1. New installer step (or extension of an existing one) that, after the repo clone:

   • Copies (or symlinks) ~/.claude/package.json to ~/.pai/package.json if not present.
   • Runs bun install in ~/.pai/ (idempotent — skip if ~/.pai/node_modules/yaml/ already exists at the right version).
   • Materializes ~/.claude/PAI/PAISECURITYSYSTEM/ into ~/.pai/PAI/PAISECURITYSYSTEM/ (analogous to per-pack skill canonicalization, but for the PAI/ subtree).

2. Decide: copy vs symlink for the PAI/ subtree. Skill packs use per-pack symlinks (Skills separation is documentation-only: Claude Code harness reads ~/.claude/skills/, not ~/.pai/skills/ #110); PAI/ has historically been a real directory under ~/.pai/PAI/ populated by other means (no current automated mechanism). Worth aligning on one model.

3. Decide: should bun.lock be tracked in the repo (commit it) or treated as a runtime-only artefact (gitignore)?

4. Test: after a fresh-install run-through, Tools/verify-security-validator.sh should report PASS=8 FAIL=0 without manual setup.

Verification

After implementation, a fresh install on a clean machine should:

• Produce a working ~/.pai/node_modules/yaml/.
• Produce a working ~/.pai/PAI/PAISECURITYSYSTEM/patterns.example.yaml.
• Allow bash Tools/verify-security-validator.sh to pass with no further setup.

Refs

• SecurityValidator silently a no-op since v4.x — restore patterns.example.yaml shipping AND make yaml resolvable from ~/.pai/hooks/ #158 (parent issue)
• Restore SecurityValidator pattern shipping and yaml manifest (#158) #159 (PR doing the runtime/Releases backport scope)
• SecurityValidator hook fires PreToolUse:Read error: missing 'yaml' package in ~/.pai/ #156 / Fix SecurityValidator yaml import crash via lazy dynamic load (#156) #157 (lazy-import fail-open that surfaced the no-op state)
• migratePerPackSymlinks in Releases/v4.0.3+/.claude/PAI-Install/engine/skill-migration.ts — pattern reference for analogous canonicalization logic.