fix: keep app-owned notify out of the protected overlay

[StarsailsClover]

Problem

notify was treated as user-owned and captured into the protected overlay. The Codex
desktop app rewrites that key with a version-scoped runtime path
(runtimes\cua_node\<hash>\...), so any captured copy goes stale the moment the app
updates.

The explicit repair command runs with manual = true and therefore merges without
requiring a clobber fingerprint (store.rs). So the sequence below silently rewrote the
live config to point at a runtime directory that no longer exists:

status : Change: Edit (score 1, threshold 4) | changed: notify
         -> "protected drift detected; run keepmyconfig repair to restore it"
repair : classification=Edit score=1  ...  overwritten notify
result : notify -> 2134bcb1950af07e   (deleted by the app update)

Effect: the turn-ended Computer Use hook stops firing, and the wrong value persists
because nothing re-reads the deleted directory.

Fix

notify now sits in the default ignored set next to mcp_servers.node_repl, which has
exactly the same lifecycle. ignored means neither protected nor restored — the key is
left to the app that owns it.

This also closes a second, worse path: ccswitch adopt published the overlay into CC
Switch's common_config_codex, so the stale runtime path would have been injected into
every future provider switch.

Evidence

Recorded reproduction against the previous binary (isolated CODEX_HOME):

step	value
baseline notify	runtime 2134bcb1950af07e
live notify after app update	runtime 81ea4d5168ddd0a3
repair	overwritten notify
result	runtime 2134bcb1950af07e restored (directory no longer exists)

After the fix, the same scenario with the freshly built binary:

Change : NoChange (score 0, threshold 4)
repair : nothing to repair
verdict: SAFE - kept the live value

Tests

• New: manual_repair_keeps_an_app_updated_notify — fails on the old behaviour.
• ignored_matches_app_owned_churn — asserts notify is ignored, and that a genuine
  user-owned registration (mcp_servers.prima-mock-api) is still protected.
• watch_repairs_a_cc_switch_style_clobber / cc_switch_adopt_publishes_common_config_providers_and_mcp
  — updated to assert app-owned churn is left alone and never published.

Verification gates

cargo fmt --all -- --check                        -> pass
cargo clippy --workspace --all-targets -D warnings -> pass
cargo test --workspace                            -> 27 passed / 0 failed
scripts/apply_watermark.ps1                       -> Inserted 0 (already compliant)

Behaviour change to be aware of

After a CC Switch clobber, notify is no longer restored from the overlay; it is absent
until the Codex app rewrites it. The failure mode changes from silently pointing at a
deleted runtime, indefinitely to briefly missing, self-healed by the owning app. Users
who maintain notify by hand can protect it again by removing it from ignored in
policy.toml.

Version

Crate 0.1.0-alpha.3, release tag v26.0-Alpha.3.