FE-1226: Split the optimizations provider into policy, errors, and storage modules

[kube]

🌟 What is the purpose of this PR?

Make the detached-run optimization provider readable. #9066 left it at 874 lines: about half was framework-free logic that happened to live next to the React state using it, and its attach loop was a single 258-line callback whose failure handling interleaved reconnect policy with state effects.

This is a pure refactor — no behavioural change, no public API change. The 17 provider tests from #9066 pass untouched, which is the guarantee that nothing moved semantically.

🔗 Related links

• FE-1226 — the reconnect work this cleans up after
• FE-1217 — parent hardening issue

🚫 Blocked by

• FE-1222, FE-1226: Classify optimization transport errors, auto-reconnect runs by id + cursor, and remove the legacy optimization path #9066 — this refactors the file that PR introduces

🔍 What does this change?

Three modules extracted from provider.tsx, all internal (nothing is added to the @hashintel/petrinaut/react entry point):

• reconnect-policy.ts — the backoff constants, reconnectDelayMs, abortableDelay, and a new pure decideAttachFailure that maps one failure to cancelled / settled / expired / reconnect / giveUp. The attach loop's 75-line catch cascade — six sequential ifs, each ending in a return, with the reconnect predicate computed inline in the middle — becomes a switch over that decision. The policy's ordering constraints are now stated where the policy lives, and testable without driving a provider through fake streams.
• transport-errors.ts — the duck-typed classifyError, buildErrorMessage, and isAbortError, plus one new isAbortFailure predicate. Run creation and the attach loop each carried their own copy of the same three-part abort check (signal.aborted || isAbortError(error) || classified?.category === "aborted"); they now share one, so they cannot drift.
• active-run-storage.ts — the sessionStorage bookkeeping for runs a reload may re-attach to. ACTIVE_RUNS_STORAGE_KEY is now imported by the tests instead of the string literal being repeated eight times.

Net effect: provider.tsx 874 → 656 lines, and runAttachLoop 258 → 163.

Also corrected in passing: the comment on computeRunningBest claimed the service "no longer knows the objective direction after the creating request ends". That was true of the old connection-scoped design; with detached runs the Optuna study — and its direction — lives for the run's lifetime. The reason the provider computes the running best is that cursors make any single attachment partial, not that the service has forgotten anything.

Pre-Merge Checklist 🚀

🚢 Has this modified a publishable library?

This PR:

• modifies an npm-publishable library and I have added a changeset file(s)

📜 Does this require a change to the docs?

The changes in this PR:

• are internal and do not require a docs change

🕸️ Does this require a change to the Turbo Graph?

The changes in this PR:

• do not affect the execution graph

⚠️ Known issues

One item from the review that produced this PR is deliberately not done: createOptimization and the reload re-attach effect duplicate ~20 lines of lifecycle (mint id → AbortController → register in two refs → prepend record → run the loop → clear both refs). Merging them needs a nullable-runId branch, because creation only learns its run id after an await while re-attach knows it upfront — the resulting helper reads worse than the duplication. Left as is.

🛡 What tests cover this?

• The 17 existing provider tests pass with no modification other than importing the storage key — the behaviour-preservation guard for the whole change.
• 10 new tests in reconnect-policy.test.ts pin the decision function: the backoff sequence and its cap, which categories reconnect, that a definitive http status never does, that cancellation outranks every other outcome, that a failure after a terminal event is settled, and that a 404 only means expired on a stored run's first attachment.

26 test files / 197 tests green in @hashintel/petrinaut; eslint and oxfmt clean.

❓ How to test this?

1. cd libs/@hashintel/petrinaut && yarn vitest --run src/react/optimizations
2. Confirm git diff on provider.tsx is only deletions plus the rewired imports and the switch.

🤖 Generated with Claude Code

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