feat(telemetry): Add squad.decisions.* OTel metrics

[diberry]

Problem

Zero squad.decisions.* metrics exist in the codebase. The decisions subsystem is completely dark — no gauges, no counters, no span attributes. You cannot detect when archival stops working or measure the token cost impact of bloated decisions.

From

Telemetry reviews of #20 and #21. Telemetry: 'The first PR should not be the archival fix — it should be the metrics.'

Proposed Metrics

Gauges (current state)

• squad.decisions.size_bytes — decisions.md file size
• squad.decisions.entry_count — number of decision entries
• squad.decisions.age_oldest_days — age of oldest active entry
• squad.decisions.inbox_depth — unmerged inbox files
• squad.decisions.archive_size_bytes — archive file size

Counters (operations)

• squad.decisions.archive_runs — Scribe archival executions
• squad.decisions.entries_archived — entries moved per run
• squad.decisions.bytes_archived — bytes recovered per run

Span Attributes (per spawn)

• agent.decisions_size_bytes on every agent spawn span
• context_utilization_pct — context window usage

Collection Points

• Coordinator session start (baseline)
• Every agent spawn (span attribute)
• Scribe run (pre/post archival)

Alerting Thresholds

• size_bytes >20KB: warn | >50KB: error
• inbox_depth >10: warn | >25: error
• archive_runs stale + size_bytes rising: error

Owner

Telemetry (Aspire & Observability)

[github-actions]

🏗️ Squad Triage — Flight (Lead)

Issue: #29 — feat(telemetry): Add squad.decisions.* OTel metrics
Assigned to: FIDO (Quality Owner)
Reason: Issue relates to testing/quality work

@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.