fix: revert deferred tool call [JAR-9208]

[JoshParkSJ]

What changed?

Moves tool confirmation from the old interrupt-based flow to the new confirmToolCall event on startToolCall, with a clean rip-and-replace of all legacy code.

https://uipath.atlassian.net/browse/JAR-9208

Changes

hitl.py (HITL approval flow):

• Removed import and usage of UiPathConversationToolCallConfirmationValue — the @durable_interrupt in ask_confirmation() now emits a plain dict instead of the old interrupt model
• Removed legacy dual-payload parsing (the {"type": ..., "value": {...}} shape from endInterrupt). Resume payloads are now always the confirmToolCall shape: {"approved": bool, "input": ...}
• Added ARGS_MODIFIED_MESSAGE constant, replacing the args_modified_by_user: True boolean with a human-readable message field in tool result metadata

messages.py (event mapper):

• startToolCall is now always emitted for confirmation tools (previously skipped). CAS reads requireConfirmation and inputSchema from this event to render the confirmation UI.
• map_tool_call_to_tool_call_start_event() accepts require_confirmation and input_schema kwargs

runtime.py:

• Added _get_tool_confirmation_schemas() to extract JSON schemas from tools marked with require_conversational_confirmation, passed to the mapper as tool_confirmation_schemas

Why rip-and-replace instead of backward compatibility?

We evaluated maintaining backward compat with the old startInterrupt/endInterrupt flow and decided against it:

1. Both sides break the old flow — backward compat is impossible at the system level. AgentInterfaces#899 removes the onInterruptStart handler from the frontend, so old interrupt events won't render. uipath-python#1558 removes emit_interrupt_event and endInterrupt handling from the bridge. Neither transition state (old Python + new CAS, or new Python + old CAS) produces a working confirmation flow — there is no graceful degradation in either direction.

2. Zero production usage. App Insights telemetry over 90 days across both jarvis-prd-eus-ais and agents-prd-appins-ne-appins confirmed: ToolCallStart count equals ToolCallEnd count (332 each, no skipped starts indicating confirmation tools), zero InterruptStartEvent traces in CAS. The @requires_approval decorator ships in the package but no deployed agent exercises it.

3. The backward compat was already dead code. The dual payload parsing in hitl.py handled the legacy {type, value} shape, but the bridge (the only thing delivering resume payloads for conversational agents) already only produces {approved, input} after uipath-python#1558. The legacy branch was unreachable.

4. Deployment is coordinated. CAS deploys first, then Python. The feature is staging-only.

See also: AgentInterfaces#899, uipath-python#1558, uipath-runtime-python#99