fix(sdk): normalize scheme-less base URLs so location query params apply

[tangtaizong666]

Issue for this PR

Closes #32077

Type of change

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

What does this PR do?

When attaching to a remote server with a scheme-less URL (opencode attach localhost:4096 --dir ., exactly the command from the issue), fuzzy search runs against the server's working directory instead of the attached client's directory.

Root cause: the SDK injects the client directory into GET requests via the rewrite() interceptor in packages/sdk/js/src/v2/client.ts, which decides whether to add the location[directory] query param by checking url.pathname.startsWith("/api/"). With a scheme-less base URL, new URL("localhost:4096/api/fs/find") parses localhost as the protocol, the pathname comes out as 4096/api/fs/find, and the check fails. The request goes out with only the flat directory param (which the v2 location middleware does not read) and the x-opencode-directory header already stripped by the interceptor, so the server falls back to its own cwd. The TUI's @ autocomplete hits /api/fs/find, hence the report. fetch resolves scheme-less URLs without complaint, so everything else keeps working and the breakage is silent.

The fix normalizes the base URL in createOpencodeClient: if it has no scheme, default to http://. URL parsing then sees the real pathname and the location params are applied as designed. Explicit http/https base URLs are untouched. Fixing it in the client (rather than in the attach command) covers every SDK consumer: attach, validateSession, run --attach.

How did you verify your code works?

Reproduced on dev: started serve in directory A, attached from directory B with attach localhost:<port> --dir <B>, typed @ in the prompt - results came from A. Server-side logging showed /api/fs/find arriving without location[directory]. Same flow with http:// worked, confirming the mechanism.

After the fix, the same scheme-less attach returns directory B's files and the request carries location[directory].

Added packages/opencode/test/server/sdk-base-url.test.ts: the scheme-less case fails without the fix (location[directory] missing) and passes with it, plus two tests pinning that explicit http/https base URLs are preserved. bun run typecheck passes in packages/sdk/js and packages/opencode; the related server test files show no new failures compared to dev.

Screenshots / recordings

Before (attach localhost:4096, server started in a different directory):

@file -> serverfile_alpha.txt        (server's cwd)
GET /api/fs/find?query=file&limit=20&directory=...   <- location[directory] missing

After:

@file -> clientfile_beta.txt         (attached client's dir)
GET /api/fs/find?query=file&limit=20&directory=...&location[directory]=...

Checklist

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