test(runtime): add main's getTitleDisplayClear to the mobile incarnation projection stub

[OrcaWin]

	Files	Added	Deleted	Net
Test	1	$\color{#1a7f37}{\Huge{\mathbf{+}}}$​1	0	$\color{#1a7f37}{\Huge{\mathbf{+}}}$​1
Prod	0	0	0	0

ELI5

A test broke when main was merged into the integration branch. The feature it protects is intact. The test's fake object was just missing a method that main started calling, so the test now provides it.

What Changed

Cause:

• main's fix(runtime): make OMP 18.4 workers ready at the composer and keep stale-title clears display-only #24295 (OMP 18.4 workers and display-only stale-title clears) added getTitleDisplayClear(ptyId) to RuntimeMobileSessionProjectionHost.
• projectRuntimeMobileSessionTabs now calls it for every terminal tab.
• The host stub in runtime-mobile-session-incarnation-projection.test.ts comes from fix(runtime): project the PTY incarnation onto mobile session tabs #24413, before fix(runtime): make OMP 18.4 workers ready at the composer and keep stale-title clears display-only #24295, and didn't have that method. All four cases threw TypeError: host.getTitleDisplayClear is not a function.

Is the fix still there? Yes:

• main itself doesn't have fix(runtime): project the PTY incarnation onto mobile session tabs #24413 any more: the Phase 3 revert (revert: take the 26 Phase 3 (#16741 port) PRs back out of main #24559) removed it there.
• After the latest main merge, OrcaWin/node-rt-phase3 still has it: runtime-mobile-session-projection.ts publishes terminalPty.incarnationId, the incarnation of the PTY that owns the issued handle.

Change: the stub gains getTitleDisplayClear: () => null, meaning no title clear is recorded. That's the neutral answer for this test, which is about incarnations, not titles.

Why

This is fixture drift, not a regression. Re-applying the projection change would have been a no-op.

Linked Issue

Fixes # (none: maintainer fix for the Phase 3 integration branch after a main merge)

Visual Proof

N/A: test fixture only.

Testing

• The incarnation projection test passes: 4 of 4.

• Mutation check: removing the incarnationId line from the projection makes it fail 2 of 4 again, so it still guards the fix.

• 30 mobile session and remote-runtime transport test files pass (214 tests).

• Scoped tsc (with declarations), oxlint, oxfmt and the changed-code quality gate pass. The lockfile is unchanged.

• I manually tested these changes locally

• Automated tests added/updated, or explained why not below

Notes

Test-only change. No product, cross-platform, SSH or mobile behaviour changes.

Checklist

• This PR is small and focused
• I explained what changed and why
• N/A for visuals with reason
• Self-reviewed for correctness, security, and performance
• Cross-platform, SSH/remote impact considered
• pnpm lint, pnpm typecheck, pnpm test, and pnpm build pass (CI will cover; targeted local runs listed above)

[pullfrog]

✅ No new issues found.

Reviewed changes

• Add missing host stub member — runtime-mobile-session-incarnation-projection.test.ts gains getTitleDisplayClear: () => null, restoring the stub to parity with RuntimeMobileSessionProjectionHost after main's #24295 started calling the method (runtime-mobile-session-projection.ts:152,154,209). This is fixture drift from the merge, not a regression; null is the neutral "no title clear" answer this incarnation-focused test does not depend on.

I ran the file: 4/4 pass. The stub is cast as unknown as RuntimeMobileSessionProjectionHost, so it typechecked even while missing the member — the failure was runtime-only, which matches the described TypeError.

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[OrcaWin]

Superseded by #24887, which carries the identical getTitleDisplayClear stub fix and is merged into OrcaWin/node-rt-phase3.