feat(T13884): pass CLEO_HOOK_PROVIDER to the goal tick

[kryptobaseddev]

cleo hook stop --provider <claude-code|codex> now spawns the goal tick with CLEO_HOOK_PROVIDER=<provider> added to the inherited environment. That lets cleo-goal tick tell which harness's Stop it is answering.

• runTickKillable(command, input, timeoutMs, provider?): when a provider is given, it sets the variable and leaves everything else in process.env as it was. processStopDispatchDeps passes the dispatcher's provider through.
• The variable name is exported once, as GOAL_TICK_PROVIDER_ENV in @cleocode/contracts/goal-runtime.js, so cleo-goal can import it. It is a const in a types-only module, so gate 10 passes.
• New test in stop-dispatch-entry.test.ts: a real tick child reports CLEO_HOOK_PROVIDER for both providers, and HOME is unchanged.

Verification

The owner directive is no local heavy runs, so CI verifies the tests and typecheck.

• Biome format and lint are clean on the three changed files.
• Gates 6 (--check), 10, 25, 38, 40 and 32 (--base origin/main) pass. CI enforces gate 39.
• The changeset lint needs a local core build, so CI's Changeset Lint verifies it.

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