refactor(b09): mount STRATEGY_RUNTIME onto RunContext during cycles

[Pigbibi]

Summary

B09 PR-2 (after #359): mount activated STRATEGY_RUNTIME onto cycle-scoped RunContext while keeping behavior-equivalent module fallback.

Changes

• run_context.py: resolve_strategy_runtime / set_active_strategy_runtime; strategy_runtime field is live (no longer reserved-only).
• _activate_execution_strategy_runtime still updates module globals (compat), returns the handle, and writes ctx.strategy_runtime when a context is bound.
• build_live_runtime stores the handle on ExecutionRuntime.strategy_runtime.
• execute_cycle mounts that handle onto RunContext.
• Cycle-path reads (evaluate / metrics / artifact candidates / periodic BTC display name) go through resolve_strategy_runtime(STRATEGY_RUNTIME).
• Tests: isolation + activate-while-bound + metrics equivalence through bound resolve.

Explicitly unchanged (B04)

• No edits to runtime_support submission / owner / runtime_call_client logic (field-only: strategy_runtime).
• No LB-HK / Firstrade / QRS Environments / secrets / Cloud Run.
• Module STRATEGY_RUNTIME symbol kept as unbound fallback (PR-3 can tighten).

Verification

.venv/bin/python -m unittest tests.test_run_context -v
.venv/bin/python -m unittest \
  tests.test_state_service \
  tests.test_trend_pool_loading \
  tests.test_cycle_service \
  tests.test_runtime_support \
  tests.test_cycle_replay_runtime \
  tests.test_strategy_runtime \
  tests.test_notify_i18n \
  -v

Local: all green (11 + 133).

Author: Pigbibi. No CloudAgent.