#15595: fix(browser): avoid local port conflicts for remote cdp

## Summary - avoid applying local CDP port-ownership conflict checks to remote CDP profiles - return the correct remote websocket reachability error when remote CDP HTTP is reachable but websocket handshake fails - add regression coverage for this branch in `server-context.remote-tab-ops.test.ts` ## Why For remote CDP profiles (e.g. Browserless), OpenClaw can currently throw: `Port <port> is in use for profile ... but not by openclaw` This is a local profile ownership error and is misleading for remote endpoints. It blocks valid remote setups before the real websocket reachability error is surfaced. ## Changes - `src/browser/server-context.ts` - handle `remoteCdp` websocket failure before local ownership conflict checks - preserve attach-target retry behavior for remote profiles - keep existing local attachOnly/local restart paths unchanged - `src/browser/server-context.remote-tab-ops.test.ts` - add regression test asserting remote websocket failures no longer produce local port-in-use ownership errors Fixes #15582 ## Validation - `pnpm check` - `pnpm build` - `pnpm vitest run src/browser/server-context.remote-tab-ops.test.ts` <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR adjusts `ensureBrowserAvailable()` in `src/browser/server-context.ts` so that remote CDP profiles (non-loopback CDP URLs) surface a remote WebSocket reachability error before running local port-ownership/"port in use" checks. It also preserves the existing attach-target retry callback for remote profiles. A regression test was added in `src/browser/server-context.remote-tab-ops.test.ts` to assert that when remote CDP HTTP is reachable but the CDP WebSocket handshake fails, the thrown error message is the remote-websocket error (and does not mention the local "Port <port> is in use" ownership conflict). Overall, the change is localized to remote CDP error ordering and does not alter local profile restart/attachOnly behavior beyond removing the remote-CDP special-casing from the local attachOnly branch (remote now always reports the remote-websocket error). <h3>Confidence Score: 5/5</h3> - This PR is safe to merge with minimal risk. - Changes are small and localized to error-path ordering in `ensureBrowserAvailable()` for remote CDP profiles, and the added test covers the previously misleading error message. No API surface changes or broad refactors were introduced. - No files require special attention _{Last reviewed commit: b7b9e77} <!-- greptile_other_comments_section --> <!-- /greptile_comment -->