fix(app): repair malformed persisted tabs

[OpeOginni]

Issue for this PR

• Closes Crash on desktop startup from null persisted tab #39644

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

• Filters null and malformed entries while persisted tabs are hydrated.
• Keeps valid session and draft tabs, including legacy tabs that need the fallback server.
• Prevents desktop startup crashes when tab consumers read the type field.

Possible Inputs:

null
// => []

[null]
// => []

[{ type: "session", sessionId: "abc" }]
// => [{ type: "session", sessionId: "abc", server: fallback }]

[{ type: "session", server: null, sessionId: "abc" }]
// => []

[{ type: "session", server: "local", sessionId: "abc" }]
// => preserved

[{ type: "draft", server: "local", draftID: "1" }]
// => removed because directory is missing

[{ type: "unknown", server: "local" }]
// => []

How did you verify your code works?

• Ran bun test --preload ./happydom.ts ./src/context/tabs.test.ts from packages/app.
• Ran bun typecheck from packages/app.
• Added regression coverage for null entries, malformed tabs, invalid top-level data, and legacy tabs.

Screenshots / recordings

• Not applicable; this changes persisted-state hydration without changing the UI.

Checklist

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