Correct context-lifecycle docs + document enforced per-fleet budgets

[indykish]

Paired with agentsfleet#506 (per-fleet budget enforcement + admin/models OpenAPI). Merge alongside it — these pages describe behaviour that PR enforces.

What changed

The context-lifecycle docs described a continuation-chain feature that was never built: the runtime re-queuing an exhausted run, a chain capping at 10, an 11th attempt labelled chunk_chain_escalate_human. None of those strings exist anywhere in the daemon or the runner. The runtime observes the context fill ratio and writes a log line; it cannot interrupt a fleet mid-loop, so it cannot force one to wrap up. A fleet that runs out of context finishes normally and the run ends processed. Nothing re-queues it.

That page also answered "Will it run forever?" with three ceilings — all fiction: the context cap only logs, the continuation cap never existed, and daily_dollars was parsed then ignored. It now names the ceilings that actually fire (wall-clock deadline, sandbox limits, tenant credit, and the per-fleet budget that agentsfleet#506 makes real).

• concepts/context-lifecycle.mdx — rewritten. Continuation chains deleted; the observe-only threshold explained; the real terminal statuses tabulated.
• fleets/authoring.mdx — the <Note> promising automatic re-enqueue replaced; the Budgets section now states both enforcement points, the two window shapes, that monthly_dollars is optional, and that a refused event is not charged.
• fleets/troubleshooting.mdx — §5 distinguishes the pre-run refusal (gate_blocked) from the mid-run stop (fleet_error, UZ-RUN-015), and budget_breach from the credit-pool labels.
• fleets/running.mdx, cli/agentsfleet.mdx — continuation:<original_actor> removed from the activity-stream tags and --actor examples; no production code writes that actor value.
• changelog.mdx — a new <Update>. The shipped entry that carried the same continuation claim is left intact (history is archived, not rewritten); the correction is published forward.

Every label, knob, and status named across the rewritten pages was checked against a non-test reader in the daemon's src/. No phantoms remain.

🤖 Generated with Claude Code

Greptile Summary

This PR corrects the docs for run lifecycle behavior and per-fleet budget handling.

• Removes the nonexistent continuation-chain behavior from lifecycle, CLI, and running docs.
• Documents context-threshold logging as observe-only behavior.
• Describes pre-run budget refusal and mid-run budget stops.
• Adds a changelog entry for the budget enforcement and documentation corrections.

Confidence Score: 5/5

This looks safe to merge.

• No blocking issues found in the changed docs.
• The budget stop code now matches the documented error-code reference.
• The no-budget wording has been corrected to describe the required daily budget and optional monthly budget.

Important Files Changed

Filename	Overview
changelog.mdx	Adds the budget enforcement update and forward correction for continuation behavior.
concepts/context-lifecycle.mdx	Rewrites run lifecycle docs around actual stop states and observe-only context checks.
fleets/authoring.mdx	Updates authoring guidance for manual continuation and fleet budget behavior.
fleets/troubleshooting.mdx	Clarifies budget refusal, mid-run stop behavior, and the related run code.
fleets/running.mdx	Removes the nonexistent continuation actor from activity-stream examples.
cli/agentsfleet.mdx	Removes the nonexistent continuation actor from event filter examples.

_{Reviews (2): Last reviewed commit: "chore: merge main into served docs branc..." | Re-trigger Greptile}

[indykish]

Paired code PR: agentsfleet/agentsfleet#506 — enforces the per-fleet budget these pages describe. Merge alongside.