feat(staging): deterministic staging-runner replacing LLM deployer on deploy-staging (ORCH-115)

Replace the LLM `deployer` agent on the `deploy-staging` stage (self-hosting
orchestrator) with a deterministic staging-runner intercepted in launch_job
BEFORE _spawn (the deploy-finalizer / post-deploy-monitor reserved-agent
precedent). The runner executes the SAME staging suite, maps the exit-code to
`staging_status:` via the existing self_deploy.map_exit_code_to_status contract,
writes 15-staging-log.md, and initiates the UNCHANGED check_staging_status gate
exactly as a finished LLM-deployer would.

Invariant (NFR-1): this replaces only the *producer* of the artifact — the
artifact contract, the gate / _parse_staging_status / check_staging_status name,
STAGE_TRANSITIONS, the machine-verdict key `staging_status:` and the DB schema are
byte-for-byte unchanged. Additive, under a kill-switch + repo-scope CSV,
never-raise, fail-safe back to the LLM path.

Two-level outcome (D5, anti ORCH-110): suite executed -> verdict -> advance
(FAILED -> the existing deploy-staging -> development rollback + developer-retry,
same as a FAILED LLM verdict); tool-error (suite did not execute) -> bounded DEFER
-> fail-closed FAILED + alert on exhaustion (infra != code fault; never a silent
advance / false green).

First implemented slice of the LLM determinization roadmap (ORCH-118 A6,
replace-deterministic-now).

- New leaf src/staging_runner.py (never-raise; proc_group tree-kill + timeout)
- launch_job intercept + _run_staging_runner_job (mirror _run_deploy_finalizer_job)
- config: ORCH_STAGING_RUNNER_* keys (enabled/repos/timeout/infra-retry budget)
- GET /queue staging_runner observability block
- docs: llm-call-sites/roadmap/usage-policy (A6 implemented; machine blocks +
  single-transport invariant intact), deployer.md (LLM branch -> fallback),
  CLAUDE.md, CHANGELOG.md, overview (tech-pipeline/tech-agents/tech-quality-security),
  .env.example
- tests/test_orch115_staging_runner.py (TC-01..TC-13); LLM anti-drift green (TC-14)

Refs: ORCH-115

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/main.py

@@ -235,6 +235,7 @@ async def queue():
     from . import lessons
     from . import checkout_hygiene
     from . import transition_lease
+    from . import staging_runner
     from .disk_watchdog import disk_watchdog
     from .build_cache_pruner import build_cache_pruner
     return {
@@ -283,6 +284,11 @@ async def queue():
         # (owner/stage/age/live) + defer/reclaim/CAS-lost counters. Additive block;
         # never-raise.
         "transition_lease": transition_lease.snapshot(),
+        # ORCH-115 (FR-7 / AC-10): deterministic staging-runner observability
+        # (read-only) — kill-switch, scope, timeout/infra budget + run/success/
+        # failed/tool_error/deferred counters, so a code-fail FAILED is distinguishable
+        # from an infra tool-error. Additive block; never-raise.
+        "staging_runner": staging_runner.snapshot(),
         # ORCH-098 (FR-4 / AC-4): lessons-journal observability (read-only) —
         # kill-switch + counts by type/status + last N lessons. Additive block;
         # never-raise (snapshot() returns {"enabled": ...} minimum on error).