feat: make devai guideline files marker-based and fully user-overridable

[markshust]

Summary

Makes marko/devai-generated AI guideline files portable across tools, single-sourced, and fully user-overridable — fixing the original bugs where AGENTS.md/CLAUDE.md were clobbered on every run and shipped dead .claude/ links into every generated project.

What changed

• Marker-aware writes. Every agent guideline file (AGENTS.md, CLAUDE.md, GEMINI.md, .github/copilot-instructions.md, junie/guidelines.md, .cursor/rules/marko.mdc) now routes through a new static GuidelinesWriter:
  • creates the file wrapped in <!-- BEGIN marko:devai --> / <!-- END marko:devai --> markers when absent;
  • on update, rewrites only the marked region — user content outside is preserved byte-for-byte;
  • if the markers are removed, devai backs off entirely (with a loud notice drained into the install log), so a user can take full ownership of any file.
• AGENTS.md is now tool-agnostic. core.md drops the dead .claude/ links and is curated to behavior-shaping rules (no-traits, interface-over-driver, constructor-injection, config-as-truth), pointing depth at the search_docs MCP tool. No static reference docs are shipped (they would drift against the MCP/LSP).
• Cursor .mdc frontmatter stays valid — markers wrap only the body, never the leading ---.
• AgentsMdRenderer no longer emits a standalone generated-by header (the marker carries that semantics); InstallationOrchestrator drains GuidelinesWriter notices into its log.
• Test hygiene: fixed a stale tests/PackagingTest.php that blanket-required every package to export-ignore its .gitignore, contradicting the deliberate skeleton behavior (commit 0ad6e90) of shipping its .gitignore to generated projects — the project template is now exempted.

Testing

Full suite green: 6935 passed, 0 failed. devai package: 217 passing.

Follow-up (not in this PR)

Live search_docs ranking could not be validated in-session (no MCP connected). A separate audit will run the greenfield query matrix against the live MCP and decide whether to adopt the docs-vec hybrid driver over docs-fts.

🤖 Generated with Claude Code