refactor(lana): use URI-safe file access

[peternhale]

PR overview

Stack 2 of 4. Depends on #951. Makes log and workspace handling URI-native so Lana can operate against local and virtual filesystems.

Changes made

• Replace filesystem paths with VS Code Uri values or serialized URI strings.
• Route reads, writes, existence checks, caching, and navigation through URI-safe services.
• Support file, memfs, vscode-vfs, and other virtual workspace schemes.
• Update log analysis, language detection, providers, source lookup, and workspace selection.
• Update URI mocks and affected unit tests.

Type of change

• Refactor

Related issues

related W-23939830

Validation

• pnpm typecheck
• Seven focused unit suites: 98 tests

[lcottercertinia]

This reads the whole file. we used to only read the first 4096 bytes to handle 100MB + logs.
We did this to support the code lenses on very large files vscode only returns document if it is less than 50MB I think (from memory) which is why we did this.

We could use the below which will give us the Uint8Array and avoid decoding the full file

const text = new TextDecoder().decode(bytes.subarray(0, 4096));

[peternhale]

Addressed as far as the current URI-safe APIs allow in 957277e. Detection now reads through workspace.fs and decodes only the first 4 KB from the returned byte array, preserving arbitrary URI providers and avoiding Node modules. workspace.fs still returns the complete byte array, so a true bounded provider read needs a future Services or filesystem-provider API; I am leaving this thread open for that remaining limitation.