fix(ci): make pi codegen hermetic to unblock the check job (Closes #160)

[pdettori]

Summary

Bumps the pi-fork submodule to a commit that makes pi's model codegen
hermetic, unblocking the check job.

Closes #160.

Root cause

The check job builds the submodule with:

- name: Build pi-fork (type declarations)
  run: cd pi-fork && npm ci && npm run build

pi's packages/ai build script regenerated src/models.generated.ts
from the live models.dev API on every build. models.dev is a moving
target: it emitted supportsReasoningEffort on a model mapped to the
openai-responses API, so the regenerated file no longer typechecked
against OpenAIResponsesCompat:

error TS2353: 'supportsReasoningEffort' does not exist in type 'OpenAIResponsesCompat'

That failed the build step, so the downstream Typecheck and Test
steps never ran — harness unit tests have not executed in CI since
2026-08-20.

Fix

Bump pi-fork → rossoctl/pi@2c28be5 (rossoctl/pi#1), which:

1. Makes the build hermetic — codegen is split out of build, so
   npm run build runs only tsgo against the committed generated files
   (no network fetch). A check:models-drift script is provided to catch
   stale generated files deliberately.
2. Widens the type — supportsReasoningEffort is added to
   OpenAIResponsesCompat so a deliberate regeneration stays valid.

No workflow changes are needed; the existing npm run build is now
hermetic by virtue of the submodule fix.

Verification

• pi: tsgo -p tsconfig.build.json on packages/ai → exit 0.
• This PR's CI should now complete the check job through Typecheck and
  Test.

Note: the submodule is pinned to the fix branch commit for CI. Once
rossoctl/pi#1 merges, the pin will be updated to the merged commit
before this PR is merged.

Assisted-By: Claude Code