feat: add lifecycle-aware compact re-entry for llmdoc

[wh1teAlter]

PR Description：

Summary

This PR makes llmdoc context loading lifecycle-aware and prevents Codex compaction from repeatedly replaying the entire startup package.

It introduces separate cold-start, resume, and compact re-entry paths, adds a compact LLMDOC_STATE contract, and keeps startup context
bounded for monolith repositories.

Motivation

Previously, the SessionStart hook matched startup, resume, clear, and compact through the same path.

Because Codex runs SessionStart(source=compact) after manual and automatic compaction, every compaction instructed the model to reload:

• the llmdoc skill
• llmdoc/index.md
• llmdoc/startup.md
• all listed MUST documents
• related task documentation

In large repositories, this repeatedly consumed the restored context window and could trigger additional compactions.

What Changed

Lifecycle-aware context loading

Lifecycle source Behavior
━━━━━━━━━━━━━━━━━━
startup, clear Perform one cold-start read of the skill and startup package
──────────────────
resume Reuse a valid LLMDOC_STATE; fall back to one cold start when unavailable or stale
──────────────────
compact Continue from the compact summary without replaying previously loaded llmdoc content

Compact re-entry now refreshes documentation only when:

• the startup fingerprint changed
• a relevant document changed
• the task enters a new subsystem
• the preserved state is insufficient
• validation or evidence conflicts

Bounded startup context

• Defines the startup package as index.md + startup.md + must/
• Adds a default 24 KiB startup-package budget
• Generates a stable fingerprint from file digests, sizes, and relative paths
• Treats the root index as an L0 router
• Recommends L1 subsystem indexes for monolith repositories
• Avoids loading a repository-wide leaf-document catalog

Codex integration

• Adds a bundled lifecycle-aware hooks/hooks.json
• Splits SessionStart into dedicated cold, resume, and compact matchers
• Produces no compact-hook output for repositories without llmdoc
• Adds an optional compact prompt template for preserving structured LLMDOC_STATE
• Keeps the more opinionated Stop hook opt-in
• Updates Stop output to the supported systemMessage shape

Validation and documentation

• Adds verify-lifecycle-hooks.sh to prevent matcher and no-reload regressions
• Documents the context lifecycle architecture and hook maintenance workflow
• Updates the core skill, init/update contracts, recorder guidance, examples, and public READMEs
• Synchronizes the Claude and Codex plugin versions to 2.3.0
• Adds a reflection capturing the original lifecycle design gap

Compatibility and Rollout

There are no breaking command or API changes.

Plugin users should note:

• Codex will require the bundled hook to be reviewed and trusted
• bundled and repo-local copies of the same hook should not be enabled together
• the compact prompt override remains optional and is not enabled automatically
• existing installations must reinstall or upgrade the plugin and start a new thread to load the new lifecycle behavior

Validation

• Lifecycle matcher and compact no-reload verification passed
• Cold-start and compact fingerprints match for the same repository state
• Non-llmdoc compact hook produces no output
• Bash syntax validation passed
• Hook and plugin JSON validation passed
• Codex plugin validation passed
• llmdoc, llmdoc-init, and llmdoc-update skill validation passed
• Startup package is 6696 bytes, below the 24576 byte budget
• English and Chinese documentation updated
• Stable llmdoc architecture, guide, routing, and reflection documents synchronized

[gemini-code-assist]

Caution

The consumer version of Gemini Code Assist on GitHub has been sunset. All code review activity has officially ceased.