fix(missions): honor configured LLM temperature for bank mission merge (#2469 follow-up)

[r266-tech]

Problem

#2469 made the internal LLM temperature configurable and its docs state the global HINDSIGHT_API_LLM_TEMPERATURE "applies to every operation" and none "drops temperature from every operation" (the documented remedy for models that reject explicit temperatures, e.g. Azure gpt-5.5, issue #2459).

But bank/folder mission merging is a 5th internal LLM call that #2469 didn't reach. _llm_merge_mission (engine/retain/bank_utils.py, scope="bank_mission", used by merge_bank_mission) still hardcodes temperature=0.3 and never reads get_config():

content = await llm_config.call(
    messages=messages, scope="bank_mission", temperature=0.3, max_completion_tokens=8192
)

So setting HINDSIGHT_API_LLM_TEMPERATURE=none (your documented fix for Azure gpt-5.5) does not cover mission merging — the 0.3 is still sent, the call raises, the try/except in _llm_merge_mission swallows it, and the merge silently degrades to naive "{current} {new_info}" concatenation. With folder missions / mission-sandbox (#2455, #2254) actively shipping, this path is gaining users following the docs and still hitting a silent failure.

Fix

Add bank_mission as a 5th per-operation temperature knob, mirroring the four introduced in #2469 (verification / retain / reflect / consolidation):

• ENV_LLM_TEMPERATURE_BANK_MISSION + DEFAULT_LLM_TEMPERATURE_BANK_MISSION = 0.3 (preserves the historical value)
• HindsightConfig.llm_temperature_bank_mission, resolved via the existing _resolve_operation_temperature (per-op env → global HINDSIGHT_API_LLM_TEMPERATURE → default 0.3)
• bank_utils.py now passes temperature=get_config().llm_temperature_bank_mission

The documented global override now genuinely covers mission merging, and none correctly omits the parameter there too. Default behavior is unchanged (still 0.3).

Docs / tests

• Documented the new knob in configuration.md and regenerated the CI-enforced skills mirror via scripts/generate-docs-skill.sh (diff is the single new row).
• test_llm_temperature_env.py: bank_mission added to _OP_FIELDS, so the default / global-override / global-none resolution cases now assert it too.
• test_llm_temperature_pipeline.py: two new tests drive _llm_merge_mission through the mock LLM and assert the bank_mission call receives 0.3 by default and None (omitted) under HINDSIGHT_API_LLM_TEMPERATURE=none.

test_llm_temperature_env.py passes locally (13 passed); the pipeline tests mirror the existing reflect/retain pipeline tests (they need the Postgres-backed memory fixture, which runs in CI).

Follow-up to merged #2469.