Consider session-type-aware prompt composition

[unforced]

Problem

All interactive chat sessions get the same PARACHUTE_PROMPT regardless of what the user is doing. A voice journal transcription session gets the same git protocol instructions as a deep coding session.

Proposed

Explore composable prompt sections that activate based on session context:

Session context	Additional prompt sections
Has working directory / code container	Git protocol, PR workflow, detailed code conventions
Voice journal	Lighter prompt, reflection-oriented
Recurring agent	Agent's own system_prompt (already works this way)
General chat	Base prompt only

This could be implemented as:

• Prompt "addenda" stored as Context nodes in the graph with activation conditions
• Simple conditional logic in _build_system_prompt() based on session metadata
• Container-level prompt extensions via core_memory (partially exists)

Context

Currently use_preset is always False — no session gets Claude Code's built-in preset. The git/PR protocol was added to PARACHUTE_PROMPT to compensate, but it's unnecessary overhead for non-coding sessions.