fix(gateway): stop actors on session delete

[ymote]

Summary

• Wire gateway slash /delete handling into the existing session-delete event channel used to stop in-memory session actors.
• Notify the runtime with the exact profiled deleted session key after the disk session clear succeeds.
• Add gateway dispatcher regressions for named deletion and current-topic deletion emitting actor-stop signals.

Closes #1219

Current-main refresh

• Base: current GitHub main / origin/main 4adbe05fff212cb85d1f0a6d6225da0713446016.
• Head: a66a2dd851659989c203f7c981ce2364e7b09dbe.
• Isolated checkout: /private/tmp/octos-1220-current.f8pao4/octos.
• Environment: Darwin 25.5.0 arm64; rustc 1.95.0; cargo 1.95.0.
• Root dirty checkout was not modified.

Local validation

• git diff --check origin/main...HEAD passed.
• cargo fmt --all -- --check passed.
• rustfmt --check crates/octos-cli/src/commands/gateway/gateway_runtime.rs crates/octos-cli/src/gateway_dispatcher.rs passed.
• typos crates/octos-cli/src/commands/gateway/gateway_runtime.rs crates/octos-cli/src/gateway_dispatcher.rs passed.
• CARGO_TARGET_DIR=/private/tmp/octos-1220-current-4adbe-target-cli CARGO_INCREMENTAL=0 CARGO_PROFILE_DEV_DEBUG=0 cargo test -p octos-cli gateway_dispatcher::tests::should_signal_actor_stop -- --nocapture passed: 2/2 matching tests.
• CARGO_TARGET_DIR=/private/tmp/octos-1220-current-4adbe-target-cli CARGO_INCREMENTAL=0 CARGO_PROFILE_DEV_DEBUG=0 cargo test -p octos-cli gateway_dispatcher::tests::should_delete -- --nocapture passed: 3/3 matching tests.
• CARGO_TARGET_DIR=/private/tmp/octos-1220-current-4adbe-target-cli CARGO_INCREMENTAL=0 CARGO_PROFILE_DEV_DEBUG=0 cargo test -p octos-cli gateway_dispatcher::tests -- --nocapture passed: 34/34 gateway dispatcher tests.
• CARGO_TARGET_DIR=/private/tmp/octos-1220-current-4adbe-target-cli CARGO_INCREMENTAL=0 CARGO_PROFILE_DEV_DEBUG=0 cargo clippy --workspace --all-targets -- -D warnings passed.
• git ls-files --others --exclude-standard was empty in the isolated checkout.

CI / merge status

• GitHub CI is green on refreshed head a66a2dd851659989c203f7c981ce2364e7b09dbe: check, check-matrix, dashboard, swarm-app, test-octos-cli, test-octos-agent (lib), test-octos-agent (integration), typos, and author-email all passed.
• PR is MERGEABLE but remains branch-protection blocked by required review (REVIEW_REQUIRED).

[ymote]

Current-main validation refresh for #1219.

Scope validated:

• Base/current main: 1fb4c88e020242d82cee245b331798ed6dc551e7 (confirmed with git ls-remote https://github.com/octos-org/octos.git refs/heads/main)
• PR head: a88f59a08b3af7d318f20316f58728dc42c1e238
• Local rehearsal merge: c5435ea46ce252b50c3223a17990a4b19d940a87
• Rehearsal clone: /private/tmp/octos-1220-current-3tLEFS (standalone clone; root checkout left untouched)
• Changed files: crates/octos-cli/src/commands/gateway/gateway_runtime.rs, crates/octos-cli/src/gateway_dispatcher.rs

Commands run:

• git fetch https://github.com/octos-org/octos.git pull/1220/head
• git merge --no-edit FETCH_HEAD clean on current local main
• git diff --check origin/main...HEAD
• rustfmt --check crates/octos-cli/src/commands/gateway/gateway_runtime.rs crates/octos-cli/src/gateway_dispatcher.rs
• cargo fmt --all -- --check
• CARGO_TARGET_DIR=/private/tmp/octos-1220-current-1fb4-test-target CARGO_INCREMENTAL=0 cargo test -p octos-cli gateway_dispatcher::tests::should_signal_actor_stop -- --nocapture
• CARGO_TARGET_DIR=/private/tmp/octos-1220-current-1fb4-test-target CARGO_INCREMENTAL=0 cargo test -p octos-cli gateway_dispatcher::tests::should_delete -- --nocapture
• CARGO_TARGET_DIR=/private/tmp/octos-1220-current-1fb4-test-target CARGO_INCREMENTAL=0 cargo test -p octos-cli gateway_dispatcher::tests -- --nocapture
• CARGO_TARGET_DIR=/private/tmp/octos-1220-current-1fb4-clippy-target CARGO_INCREMENTAL=0 cargo clippy -p octos-cli --lib --no-deps
• CARGO_TARGET_DIR=/private/tmp/octos-1220-current-1fb4-clippy-api-target CARGO_INCREMENTAL=0 cargo clippy -p octos-cli --features api --lib --no-deps
• git ls-files --others --exclude-standard

Results:

• Rehearsal merge was clean.
• git diff --check passed.
• Touched Rust files passed rustfmt --check.
• Focused actor-stop regressions passed: 2/2.
• Focused delete command regressions passed: 3/3.
• Full gateway_dispatcher::tests passed: 34/34.
• Both clippy commands exited 0; the API clippy run emitted existing warnings outside this slice.
• git ls-files --others --exclude-standard returned empty in the rehearsal clone.
• Environment: Darwin 25.5.0 arm64, rustc 1.95.0, cargo 1.95.0.

Current-main blocker found:

• Full cargo fmt --all -- --check fails outside this PR diff on current-main formatting drift in:
  • crates/octos-agent/src/agent/loop_runner.rs
  • crates/octos-agent/src/loop_detect.rs
  • crates/octos-cli/src/api/ui_protocol_ledger.rs
• The touched files for this PR passed formatting.

Issue fit:

• Gateway /delete now emits the same profiled session-delete signal consumed by the runtime to stop the in-memory session actor after disk deletion succeeds.
• Tests cover deleting a named session and deleting the current named session, including the emitted actor-stop signal.

Remaining gap:

• GitHub reports this PR as MERGEABLE but REVIEW_REQUIRED / BLOCKED, so I did not merge.