feat(context-compression): add missing integration points for Focus Agent, SideQuest, and SWE-Pruner

[bug-ops]

Context

PR #1900 (feat(core): context compression — Focus Agent, SWE-Pruner/COMI, SideQuest) deferred the following integration points. These were explicitly acknowledged as missing by the implementation review.

Missing integration points

1. CLI flags in src/main.rs

• --focus / --no-focus — enable/disable Focus Agent at startup (overrides [agent.focus] enabled)
• --sidequest / --no-sidequest — enable/disable SideQuest eviction at startup (overrides [memory.sidequest] enabled)
• --pruning-strategy <reactive|task_aware|mig|task_aware_mig> — override [memory.compression] pruning_strategy

2. --init wizard steps

• Add a Context Compression section to the interactive config wizard:
  • "Enable Focus Agent?" (default: no) → [agent.focus] enabled
  • "Focus compression interval (turns)?" → [agent.focus] compression_interval
  • "Enable SideQuest eviction?" (default: no) → [memory.sidequest] enabled
  • "SideQuest eviction interval (turns)?" → [memory.sidequest] interval_turns
  • "Pruning strategy?" (reactive / task_aware / mig / task_aware_mig) → [memory.compression] pruning_strategy

3. Debug dump output

When --debug-dump is enabled, emit structured files for:

• {n}-pruning-scores.json — per-block relevance/redundancy/MIG scores from score_blocks_task_aware / score_blocks_mig
• {n}-focus-knowledge.txt — current contents of the Knowledge block after each complete_focus
• {n}-sidequest-eviction.json — SideQuest prompt + LLM response + applied cursor indices for each eviction pass

4. TUI spinners for background operations

Per TUI rules: any background or implicit operation must be accompanied by a visible system status indicator with a spinner.

• Spinner during extract_task_goal() LLM call: Extracting task goal…
• Spinner during SideQuest background LLM call (spawned via tokio::spawn): SideQuest: scoring tool outputs…
• Status update after SideQuest eviction applies: SideQuest evicted N tokens

Acceptance criteria

• --focus / --sidequest / --pruning-strategy CLI flags in src/main.rs
• --init wizard section for context compression options
• --debug-dump emits pruning-scores, focus-knowledge, and sidequest-eviction files
• TUI spinners for goal extraction and SideQuest background LLM calls
• All four points covered by appropriate tests or manual verification

References

• PR feat(core): context compression — Focus Agent, SWE-Pruner/COMI, SideQuest (#1850, #1851, #1885) #1900
• Architecture: #1850, #1851, #1885
• Review handoff: .local/handoff/ in the context-compression worktree