fix(clarify): show decision context and compact Discord choices

[RunLittleTurtle]

Summary

• require an explicit, self-contained context for model-generated clarify prompts
• render that context above the focused question on every platform callback
• keep the full canonical choices visible as a numbered list in Discord message content and embeds
• label Discord buttons with the matching number and a compact action label (1 · Approve) instead of numbers alone or clipped explanations
• preserve the full original choice as the callback value after a click
• use secondary button styling for equal-significance choices, following Discord guidance
• document the native prompt contract and add regression coverage across the tool, executor, Discord, Telegram, and gateway

Why

Discord mobile clients truncate long button labels well before the API's 80-character limit. More importantly, a clarify card could previously ask the user to approve “the diff shown” or “this proposal” even when that context was only present in the agent's internal reasoning. The user then saw clipped controls without enough visible information to make an informed choice.

The new contract separates the two responsibilities:

• message body: complete context plus full numbered options
• controls: the same number plus a short action label

Choices use the format Short label — full explanation, so the relationship stays obvious while the canonical value remains unchanged.

Community credit

This branch includes and preserves the author commit from #62291, which introduced the full numbered choice list and numeric controls after repeated real-user reports. This PR extends that work with explicit decision context and meaningful compact button labels.

Related reports and prior work: #37134, #41353, #60245, #62291.

Compatibility

• context is appended to the Python helper signature, so existing positional callback callers remain compatible.
• model-facing tool calls require context in the schema.
• multiple-choice calls that bypass the schema fail closed when context is missing.
• open-ended direct Python callers remain backward-compatible.
• Telegram's existing full-choice rendering remains unchanged and covered by tests.

Verification

101 tests passed, 0 failed

Command:

scripts/run_tests.sh \
  tests/tools/test_clarify_tool.py \
  tests/tools/test_clarify_gateway.py \
  tests/gateway/test_discord_clarify_buttons.py \
  tests/gateway/test_discord_prompt_content_siblings.py \
  tests/gateway/test_telegram_clarify_buttons.py \
  tests/gateway/test_clarify_active_session_bypass.py \
  tests/run_agent/test_tool_call_guardrail_runtime.py -q

Additional checks:

• ruff check on all changed Python files: pass
• python -m py_compile on production modules: pass
• git diff --check: pass