[STG-2464] ci: gate v3 SEA binary build on server changes

[shrey150]

What & why

build-server-sea (Build SEA binary (tests, v3)) was the only package-scoped job in ci.yml without a path-filter gate. It only declared needs: [run-build], so it compiled the stagehand-server-v3 single-executable (SEA) across all 6 platforms + a sourcemap build on every PR — including metadata-only release PRs that touch zero server code (e.g. the browse version-bump PR #2287, where core / server-integration / e2e / evals all correctly skipped but the SEA build still ran).

This adds the same gate its siblings already use:

  build-server-sea:
    needs: [run-build, determine-changes]
    if: needs.determine-changes.outputs.server == 'true'

The server filter matches packages/server-v3/**, packages/server-v4/**, packages/core/**, root package.json, the lockfile, pnpm-workspace.yaml, and ci.yml — so genuine server changes still build. The only downstream consumer, server-integration-tests, already runs solely when server == true (via discover-server-tests), so gating is safe: when server is unchanged, both skip together; a skipped job passes branch protection.

Linear: STG-2464

E2E Test Matrix

Command / flow	Observed output	Confidence / sufficiency
ruby -ryaml -e "YAML.load_file('.github/workflows/ci.yml')"	YAML OK	Proves the workflow still parses after the edit.
git diff --stat origin/main..HEAD	.github/workflows/ci.yml | 3 ++- (1 file, +2/-1)	Confirms the change is scoped to a single job, no collateral edits.
This PR's own CI run	build-server-sea runs (not skipped)	Live proof the gate doesn't over-skip: ci.yml is itself in the server filter, so server == true here and the SEA build correctly fires.
Cross-check vs PR #2287 (browse@0.9.2, metadata-only)	On #2287 determine-changes.server == false — evidenced by core / server-integration / e2e / evals all showing skipped while SEA still built	Establishes the exact scenario this fixes; after merge, such a PR would skip build-server-sea too. Not directly runnable pre-merge (would need the merged workflow on a metadata-only PR).

🤖 Generated with Claude Code

---

Summary by cubic

Gated the build-server-sea job to run only when server changes are detected. This stops unnecessary multi-platform SEA builds on metadata-only PRs and stays aligned with sibling jobs; server-integration-tests remains in lockstep. Linear: STG-2464.

• Bug Fixes
  • In .github/workflows/ci.yml, updated build-server-sea to needs: [run-build, determine-changes] and added if: needs.determine-changes.outputs.server == 'true'.

^{Written for commit 8cda7c3. Summary will update on new commits.}

[changeset-bot]

⚠️ No Changeset found

Latest commit: 8cda7c3

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[cubic-dev-ai]

No issues found across 1 file

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

_{Re-trigger cubic}