Gate git watcher behind auto_watch config (contained indexing)

[Andy11-cpu]

Summary

Split from the original bundled PR per review feedback. This PR covers auto_watch only; sibling PRs handle the other changes:

• Tier RAM budget by host size #752 — RAM budget tiering (25% / 35% / 50%)
• Make install hooks opt-in via --hooks #753 — Install hooks opt-in (--hooks)
• Deduplicate project indexes by git/path identity #754 — Project index deduplication by git/path identity (merge before this PR)

This PR

• Add auto_watch config (default false)
• Do not register the git watcher on MCP initialize unless auto_watch is enabled
• Re-index only via index_repository, or when auto_watch is turned on after a manual index
• index_repository registers the watcher only when auto_watch is enabled

Motivation

On multi-project setups, registering the git watcher on every MCP connect caused background re-index storms even when auto_index was false.

Test plan

• cli_config_get_bool covers auto_watch default false
• mcp_auto_watch_disabled_skips_watcher_on_connect in test_mcp.c
• make -f Makefile.cbm test passes (CI)
• MCP connect with existing index: watcher.skip (not watcher.watch) when auto_watch=false

Signed-off-by: Andy11-cpu canada11@duck.com

[DeusData]

Huge thanks for opening this PR and for the work you put into it.

The maintainer shop is currently full, so this may sit for a bit before it gets a proper review. We will come back to this as soon as possible with real feedback; I wanted to make sure it did not sit unacknowledged in the meantime.

[DeusData]

Thanks. This bundles several independent behavior changes: auto_watch, project deduplication, RAM tiering, and hook opt-in defaults. Please split these or link focused tracking issues for each. Also please remove generated/co-author/session attribution trailers from non-merge commits. Because this changes MCP initialization/watchers and install defaults, each behavior needs focused tests and CI evidence.

[Andy11-cpu]

Thanks for the review — addressed all three points:

1. Split into focused PRs

• Tier RAM budget by host size #752 — RAM budget tiering (25% / 35% / 50%)
• Make install hooks opt-in via --hooks #753 — Install hooks opt-in (--hooks)
• Deduplicate project indexes by git/path identity #754 — Project index deduplication by git/path identity
• Gate git watcher behind auto_watch config (contained indexing) #625 (this PR, updated) — auto_watch gate only; stacks on Deduplicate project indexes by git/path identity #754

2. Removed co-author / session attribution trailers
Non-merge commits now have a single Signed-off-by line only (no Co-authored-by: Cursor).

3. Focused tests per behavior

• RAM tiers: mem_ram_fraction_* in test_mem.c (Tier RAM budget by host size #752)
• Hooks opt-in: cli_install_plan_hooks_opt_in_default in test_cli.c (Make install hooks opt-in via --hooks #753)
• Project dedup: test_project_resolve.c (Deduplicate project indexes by git/path identity #754)
• auto_watch: mcp_auto_watch_disabled_skips_watcher_on_connect + config default test (Gate git watcher behind auto_watch config (contained indexing) #625)

CI should run on each PR independently. Happy to adjust merge order if you prefer a different stack.