fix(backend): abort no-progress unattended runs and lower maxSteps defaults

[willdady]

Closes #268.

Problem

A trigger/scheduled (unattended) agent run that fails to converge — repeatedly issuing the same tool call and getting the same result with no resulting state change — keeps going, with context and token cost growing every step, until it hits maxSteps. The only backstop today is the step ceiling, and the defaults are poorly chosen (create form 30; backend fallback for an agent with no explicit value is 1). This is most likely on weaker self-hosted models (vLLM/Ollama).

Changes

No-progress detection (unattended runs only) — apps/backend/src/runs/no-progress.ts

• A run-scoped, in-memory detector tracks a signature per tool call: tool name + a stable normalized serialization of its arguments + a hash of the result.
• Aborts when the same full signature recurs K = 3 times within the run, even when other calls are interleaved (occurrences need not be consecutive).
• The result is part of the signature, so a repeated call whose result differs (e.g. a board re-read after an intervening write that changed it) is legitimate progress and does not count.
• Strictly intra-run and in-memory: recomputes counts from the steps the AI SDK already accumulates on each stop-condition evaluation. No external store; no state crosses a run/process boundary.
• Wired as an additional stopWhen condition included only on the headless generate path (the trigger/scheduled execution path). Interactive/streamed runs are untouched.
• On trip, the run is recorded as failed with a machine-readable no_progress: reason naming the repeated tool and count (persisted to triggerRun.errorMessage), and the abort is logged. It does not appear as a successful run.
• Fail-safe: if a result legitimately differs every call (volatile timestamps etc.), signatures never collide, the detector under-counts, and the step ceiling remains the backstop — rather than risk a false abort.

Lower maxSteps defaults

• New-agent create form default 30 → 15 (apps/frontend/components/agent-form.tsx).
• Backend fallback for an agent with no explicit maxSteps 1 → 15 (DEFAULT_AGENT_MAX_STEPS in chat-execution.ts).
• maxSteps stays the single user-owned ceiling everywhere — no separate clamp for triggered runs.

Tests

• no-progress.test.ts — interleaved same-result abort at K; changing-result no-abort; result-in-signature; arg-key-order normalization; distinct-args no-collision; custom + default threshold; sticky once tripped; NoProgressError shape.
• agent-runner.test.ts — unattended generate records a no_progress failure when it trips; no abort when results change; interactive stream has no no-progress condition.
• chat-execution.test.ts — agent without an explicit maxSteps resolves to 15.

pnpm typecheck, pnpm lint, and the full backend suite (974 tests) pass.

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