[FEATURE] Programmatic access to scheduled routine (cloud session) transcripts via API

Use case

Retrieve the step-by-step transcript/trace of a scheduled routine run programmatically — for audit records, observability pipelines, and cost attribution — instead of only via the web UI.

Current behaviour

• The routines /fire API returns only claude_code_session_id and claude_code_session_url — no transcript, logs, or summary in the response body.
• The only way to read a cloud routine run's trace is to open the session in the web UI and copy it manually.
• Local interactive sessions write JSONL transcripts under ~/.claude/projects/<slug>/, but cloud/scheduled routine runs have no equivalent accessible artefact — not downloadable, not API-fetchable, not synced.
• Hooks don't cover this (local-only; cloud routines don't trigger them), and no OpenTelemetry export is documented for routines.

Desired behaviour

Either:

• A REST endpoint, e.g. GET /v1/claude_code/sessions/{session_id}/transcript (auth via API key or per-routine token), returning transcript JSONL or a structured trace (tools used, files read, commands run, final summary); or
• The /fire response (and routine run records) carrying a fetchable transcript_url.

Why it matters

• Audit and compliance: organisations running fleets of scheduled routines need a durable record of what each run did, retrievable by systems rather than humans.
• Observability: correlating routine runs with logs/metrics currently requires manual UI archaeology.
• Cost attribution: no way to analyse token/time per routine programmatically.

Workaround we use today

Each routine's prompt calls a custom telemetry MCP tool at session end with run metadata and a pointer to the session URL. It works, but it's self-reported by the model rather than harness-recorded, so it can't serve as an audit-grade transcript.

Related (adjacent, none covering this): #80732 (programmatic usage data), #76103 (routines setting session titles), anthropics/claude-agent-sdk-typescript#14 (SDK session history).