[ChechiDev]

Summary

• Adds sw_keepalive_confirmed gate immediately after extension_config_inject, before target navigation
• Gate reaches the extension SW via CDP and verifies swKeepalive alarm exists using chrome.alarms.get()
• If SW is unreachable or alarm is missing, run blocks at the new gate with sanitized evidence — no longer wastes the full 300s observation window
• Evidence is sanitized: only sw_keepalive_alarm_present (bool/None) and sw_keepalive_alarm_error_type (str on failure)

Motivation

Real smoke on v0.47.6 blocked at clearance_observed with extension_diagnostic: unavailable / no SW target found. The swKeepalive alarm (added in v0.47.6) may not be created before observation begins. This gate surfaces that failure fast.

Changes

• infrastructure/browser/pydoll_engine.py — async read_extension_alarm(alarm_name) (CDP, argument as value — no injection risk; per-step timeout 2s)
• cli/real_clearance_composition.py — make_sw_keepalive_checker(engine, loop) factory (10s outer timeout)
• cli/smoke_clearance_real.py — GATE_SW_KEEPALIVE_CONFIRMED gate (PASS/BLOCKED/unreachable paths)
• cli/main.py — factory wired into harness.run() on --real-clearance path
• 13 new unit tests covering all paths; 4 review lenses APPROVED after fixes

Test plan

• All 13 new unit tests pass (TestReadExtensionAlarm, TestMakeSwKeepaliveChecker, TestSwKeepaliveConfirmedGate)
• Full unit suite passes
• Ruff + flake8 clean
• No real smoke executed

Closes #201