feat: Generate decisions-index.md as separate summary file

[diberry]

Problem

decisions.md has no compact summary. Agents must read the full file. An index inside the file fights the union merge driver (Scribe rewrites a section = mutable-in-place on an append-only file).

From

Flight review of #20 (A2 critique), Procedures review of #20.

Proposed

1. Scribe generates decisions-index.md as a SEPARATE file (not inside decisions.md)
2. Index format: compact table with Date | Topic | Status | By | Domain
3. Regenerated wholesale on every Scribe merge (not append-only — full rewrite is safe)
4. Spawn prompts reference the index for lightweight context
5. Agents read index only; full decisions.md available on-demand
6. Enables degraded mode: if decisions.md >50KB, agents read index only

Benefits

• Union merge safe (index is regenerated, not appended)
• ~2KB overhead vs ~86K for full file
• Enables coordinator filtering (issue TBD)

Owner

EECOM (Core Dev) + Procedures (Prompt Engineer)

[github-actions]

🏗️ Squad Triage — Flight (Lead)

Issue: #28 — feat: Generate decisions-index.md as separate summary file
Assigned to: Flight (Lead)
Reason: No specific domain match — assigned to Lead for further analysis

@copilot evaluation: No strong capability match — routed to squad member.

Team roster:

• Flight (Lead) → label: squad:flight
• Procedures (Prompt Engineer) → label: squad:procedures
• EECOM (Core Dev) → label: squad:eecom
• FIDO (Quality Owner) → label: squad:fido
• PAO (DevRel) → label: squad:pao
• CAPCOM (SDK Expert) → label: squad:capcom
• CONTROL (TypeScript Engineer) → label: squad:control
• Surgeon (Release Manager) → label: squad:surgeon
• Booster (CI/CD Engineer) → label: squad:booster
• GNC (Node.js Runtime) → label: squad:gnc
• Network (Distribution) → label: squad:network
• RETRO (Security) → label: squad:retro
• INCO (CLI UX & Visual Design) → label: squad:inco
• GUIDO (VS Code Extension) → label: squad:guido
• Telemetry (Aspire & Observability) → label: squad:telemetry
• VOX (REPL & Interactive Shell) → label: squad:vox
• DSKY (TUI Engineer) → label: squad:dsky
• Sims (E2E Test Engineer) → label: squad:sims
• Handbook (SDK Usability) → label: squad:handbook
• Ralph (Work Monitor) → label: squad:ralph
• @copilot (Coding Agent) → label: squad:copilot

To reassign, remove the current squad:* label and add the correct one.

[diberry]

Closing: work completed upstream or no longer relevant. See diberry/project-dina#22 cleanup audit.