install never updates an existing instruction block: improvements to CLAUDE.md/AGENTS.md guidance never reach existing users

[tirth8205]

_inject_instructions (code_review_graph/skills.py:1451) is append-only with a marker guard:

if marker in existing:
    logger.info("%s already contains instructions, skipping.", file_path.name)
    return False

It never compares content. Once the marker is in a file, no later release can change that section. Reinstalling is a no-op.

Impact

Every improvement to the injected instruction text only reaches brand-new installs. Everyone who installed at any earlier version keeps the original wording forever, including the unguarded "ALWAYS use the graph BEFORE using Grep/Glob/Read" phrasing that #314 is about. Since the text steers agent behavior in every session, this silently pins existing users to whatever guidance shipped the day they installed.

Reproduction

On a checkout that has the marker in CLAUDE.md, run the install path with a modified section:

from pathlib import Path
from code_review_graph.skills import inject_claude_md, inject_platform_instructions
inject_claude_md(Path('.'))
inject_platform_instructions(Path('.'))

CLAUDE.md, AGENTS.md, GEMINI.md and the two .github copilot files are left byte-identical even though the generated section differs. Only files that did not exist yet get written.

Why it is not a one-line fix

The generated section has an opening marker and no closing marker, so its end boundary is implicit. Replacing to end of file would eat user-authored content that follows the block. A correct fix needs an explicit end marker for new writes, exact-match replacement of known historical section variants for legacy blocks, and a refusal that preserves the file and tells the user when the block has been hand-edited. There is precedent for that exact-match approach in _remove_legacy_instruction_file.

Same failure class as the still-open upgrade half of #558, where reinstall leaves stale hook blocks alongside new ones.

Being fixed alongside #314.

[tirth8205]

Fixed in #886 (merged as d9c5f04).

Generated sections now carry a closing marker so they have real boundaries. Blocks written by earlier releases have none, so _upgrade_managed_block matches their full recorded text, longest first, and never guesses where a boundary-less block ends. code_review_graph/_legacy_instructions.py records the 10 past variants, recovered both from the git history of skills.py and by scanning the instruction files this repo ships. The second source mattered: this repo's own CLAUDE.md, AGENTS.md and GEMINI.md carried a block a markdown formatter had reflowed, a shape the generator never produced, and those three would otherwise have been misreported as hand-edited and skipped.

_inject_instructions now reports created, updated, unchanged or conflict. A hand-edited block is left exactly as written and named in the output. An unchanged file is not rewritten at all, so reinstall does not touch its mtime. uninstall had the same bug in reverse, refusing to remove blocks written by older releases, and now consults the same recorded list.

Verified end to end rather than only in tests: this repository's own instruction files were upgraded through the real install path, with every byte outside the managed block confirmed identical.