docs: link on-demand agent lifecycle doc from README and arch overview [doc-updater]

[james-in-a-box]

Update documentation to reflect changes from #3181 (slice-3 of #3064):

Slice-3 wired JobSupervisor into the orchestrator event loop and added orchestrator/supervision_policy.py as the single source of truth for supervision constants (backoff factor, cap, warn/alert thresholds). These files are now part of the Multi-Agent Orchestration component. A companion architecture doc, on-demand-agent-lifecycle.md, was added in this set but was not yet linked from docs/architecture/README.md or README.md.

Changes:

• docs/architecture/README.md: add event_loop.py and supervision_policy.py to the Multi-Agent Orchestration components row; add On-Demand Agent Lifecycle to the Key Architectural Decisions list
• README.md: add on-demand-agent-lifecycle.md link alongside orchestrator.md in the documentation table

Triggered by: #3181

Test Plan

• Automated: doc-only changes, no tests needed
• Manual: verify links resolve in rendered GitHub markdown

Authored-by: egg

[egg-reviewer]

No agent-mode design concerns. This is a doc-only change adding two markdown links to the On-Demand Agent Lifecycle architecture doc — no prompts, pre-fetching, output schemas, LLM API calls, or model identifiers in scope.

— Authored by egg

[egg-reviewer]

Approve. Doc-only change. I traced every claim in the diff against the repo and everything resolves correctly.

Verification performed

Link targets exist and resolve:

• docs/architecture/on-demand-agent-lifecycle.md exists (12.8 KB). The new link in README.md uses the repo-root-relative path docs/architecture/on-demand-agent-lifecycle.md ✓; the link in docs/architecture/README.md uses the same-directory relative path on-demand-agent-lifecycle.md ✓.
• All four files listed in the Multi-Agent Orchestration components row exist: concurrent_executor.py, kubernetes_spawner.py, and the two newly-added event_loop.py + supervision_policy.py.

Descriptions are accurate, not aspirational:

• JobSupervisor referenced in the arch-README description is a real class (orchestrator/event_loop.py:237), wired in via slice-3 as the body states.
• The "streak/backoff/alert via shared supervision_policy.py" claim matches the source: SUPERVISION_BACKOFF_FACTOR=2, _CAP_SECONDS=30, _STREAK_WARN=5, _STREAK_ALERT=10, consistent with the doc's own supervision table (streak × 2 s, capped 30 s, sticky alert at ≥10).

No duplication / scope is correct:

• The doc was already linked from docs/index.md:35 (pre-existing, untouched). This PR correctly adds only the two locations that were missing — README.md and docs/architecture/README.md — matching the body's claim that the doc "was not yet linked from" those two files.

Markdown integrity: both edited table rows retain correct column counts; the ·-separated multi-link cells follow the existing convention already used in the same tables (e.g. the "Non-Claude model routing" row).

No blocking or non-blocking issues found.

— Authored by egg

[james-in-a-box]

egg review completed. View run logs

1 previous review(s) hidden.