fix(app): correct "sesssion" typo in LayoutRoute tag

[avneeshjadhav04]

Issue for this PR

Closes #40421

Type of change

• Bug fix

What does this PR do?

Fixes a misspelled LayoutRoute discriminated-union tag: dir-new-sesssion (triple "s") -> dir-new-session, in packages/app/src/context/layout.tsx and its consumers.

The tag represents navigating to /<dir>/session without a session id (a new session about to be created in that directory). It is derived from the URL via currentRoute() on every render and is never persisted, so the rename is behavior-neutral — but any future consumer writing dir-new-session would silently never match the misspelled tag.

Changed 4 occurrences in 3 files:

• packages/app/src/context/layout.tsx (type definition + constructor)
• packages/app/src/components/titlebar.tsx
• packages/app/src/components/settings-v2/dialog-settings-v2.tsx

How did you verify your code works?

• bun typecheck in packages/app passes
• Repo-wide typecheck passes (pre-push hook, 36 packages)
• No remaining sesssion matches in the repo

Screenshots / recordings

Not applicable — internal identifier rename, no UI change.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR