Clamp packet ranges and make handoff metadata optional

[TheCryptoDonkey]

Model-free retrieval analysis of the 98 recorded experiment cells (docs/experiments/retrieval-recall-20260923/):

• Every arm usually retrieves all required evidence (mean recall 0.90 plain, 0.96 Graphify, 0.92 Context); three quarters of full-recall answers are still rejected, so acceptance on these tasks measures synthesis, not retrieval.
• The Context arm's measurable friction is tool errors: 71 across its cells, one call in five on DeepSeek.

repository_packet through MCP (CLI spec unchanged):

• an endLine past the end of a file reads to its last line; originalSpec records the range read so verifyPacket rebuilds it exactly; a range starting past the end is still rejected;
• only sources is required; blank or omitted handoff metadata gets a neutral task and acceptance check;
• a plan anchor outside every block points at mode: "build".

Checks: npm run check (182 context-tools tests), navigation smoke, both benchmark gates with recall 1.0.

🤖 Generated with Claude Code

https://claude.ai/code/session_01KzXbuBSq88i3Re82qt6c4L