[BUG] Windows desktop: Claude_Browser MCP server registers zero tools since ~v2.1.229 (worked through v2.1.227)

## Summary

On the Windows desktop app, the desktop-internal `Claude_Browser` MCP server (the one backing the Code tab's Browser pane) registers **zero tools** into sessions. None of `mcp__Claude_Browser__*` are exposed — not as loaded tools, not in the deferred-tool list.

This is a regression. The same server worked normally on the same machine, in the same project, through **v2.1.227**, and has produced zero tool calls in every session since **v2.1.229**.

Other desktop-native MCP servers in the same session are unaffected: `computer-use`, `scheduled-tasks`, `ccd_session_mgmt`, `ccd_directory`, and `claude-in-chrome` all register normally. It is specifically `Claude_Browser` that is missing, which distinguishes this from #87098 (where *no* desktop-native servers load in `sdk-cli` sessions).

## Environment

- Claude Code **v2.1.258** (read from the session transcript's `version` field)
- Claude desktop app, Code tab, native local session (not `sdk-cli`, not SSH/WSL)
- Windows 11 Home 10.0.26200
- Project: a local Next.js site repo, running in a git worktree

## Expected

`mcp__Claude_Browser__navigate`, `__preview_start`, `__preview_list`, `__computer`, `__read_page`, `__get_page_text`, `__find`, `__form_input`, `__javascript_tool`, `__read_console_messages`, `__read_network_requests`, `__tabs_*`, `__resize_window`, `__preview_stop`, `__preview_logs` are available to the session, as they were on v2.1.227.

## Actual

**Probe 1 — direct select by name:**

Query: `select:mcp__Claude_Browser__navigate,mcp__Claude_Browser__preview_start,mcp__Claude_Browser__computer`

Response, verbatim:

```
No matching deferred tools found
```

**Probe 2 — keyword search** (`browser pane preview navigate screenshot`, max_results 15):

Returns 15 tools, all from other servers — `mcp__claude-in-chrome__*` (navigate, browser_batch, computer, find, read_console_messages, resize_window, tabs_context_mcp, tabs_create_mcp, upload_image, gif_creator, select_browser, switch_browser, list_connected_browsers), `mcp__computer-use__computer_batch`, plus `DesignSync` and `WebFetch`.

**Zero `mcp__Claude_Browser__*` entries.** The session-start deferred-tool list likewise contains none.

## Evidence that this is a version regression, not a config change

I scanned all ~305 local session transcripts under `~/.claude/projects/` and counted real `tool_use` invocations of `mcp__Claude_Browser__*`:

| Version range | Claude_Browser tool calls |
|---|---|
| v2.1.202 → v2.1.227 | 3,399 (last call 2026-08-12, on v2.1.227) |
| v2.1.229 → v2.1.258 | **0**, across ~1,290 sessions |

Restricting to web/frontend projects, where the Browser pane is actually useful:

- On v2.1.219: 66 of 351 such sessions used the browser tools (~19%)
- After v2.1.229: **0 of 270**

The specific project I probed above is one where it demonstrably worked — 21 sessions used these tools, several with 20–35 calls each, most recently 2026-08-12 on v2.1.227. Nothing about that project's MCP configuration changed in between.

So the drop is not "users stopped reaching for it": the capability probe above shows the tools are **not registered**, in a project with a documented working baseline.

## Steps to reproduce

1. Windows desktop app, Code tab, open a local project as a normal (non-`sdk-cli`) session on v2.1.258.
2. Ask the session to search its deferred tools for `mcp__Claude_Browser__navigate`.
3. Observe `No matching deferred tools found`, while `mcp__claude-in-chrome__*` and `mcp__computer-use__*` resolve fine.

## Possibly related

There is a cluster of open Windows reports where the Browser pane crashes the GPU process or the whole app: #91290, #90892, #90418, #87013, #81749. My exact OS build (10.0.26200) appears in one of them.

I have **not** established a causal link — I don't know whether the server was deliberately gated off on Windows in response to those crashes, or whether it regressed silently. If it was an intentional mitigation, saying so in the release notes would help; right now the tools simply vanish with no message, and docs/project instructions that reference `preview_*` become silently wrong.

## Impact

Any project guidance that says "use the `preview_*` tools to verify changes" is dead on current versions. The workarounds (`playwright-cli`, a Playwright test suite, or the `claude-in-chrome` extension) all work but are heavier, and `claude-in-chrome` drives the user's real browser rather than an embedded pane.

Reproduce the missing Claude_Browser tools on Windows desktop v2.1.258, then compare registration behavior with v2.1.227 and the unaffected native MCP servers. Trace the Claude_Browser registration path and any Windows gating introduced between those versions. Done means the named Claude_Browser tools register again, or the intentional limitation is clearly surfaced and documented.

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