Add resilience primitives: RetryPolicy, CircuitBreaker, AC_circuit_call

[JE-Chen]

Remaining-backlog batch 15 — reusable resilience primitives, full layers + tests + EN/Zh v25 docs + README.

Features (utils/resilience, pure-stdlib)

• RetryPolicy / retry_call — retry a callable on configured exceptions with exponential backoff (injectable sleep). Reusable wrapper; the existing AC_retry flow command already covers retrying an action body, so this adds the programmatic primitive (no duplicate executor command).
• CircuitBreaker / CircuitOpenError — open after N consecutive failures, short-circuit until reset_timeout, half-open trial (injectable clock). New AC_circuit_call / ac_circuit_call runs an action list through a named breaker → {state, record}.

Note

Discovered AC_retry already exists as a flow-control block command (exec_retry); dropped the redundant/colliding retry command and kept RetryPolicy as a facade primitive.

Verification

• 7 tests pass (retry success-after-flakes + backoff growth + exhaustion, breaker open/short-circuit/half-open/close with fake clock, wiring); ruff clean; radon no CC≥C; bandit clean; PySide6-free.

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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🟢 Metrics 37 complexity · 0 duplication

Metric	Results
Complexity	37
Duplication	0

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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