Normalize both the candidate and terminal.cwd before the remote-POSIX
containment check so `{cwd}/../other/...` lexical escapes are rejected, and
restore the blocked-system-root gate BELOW the home-directory allow-list in
both resolve_trusted_workspace() and validate_workspace_to_add() so valid
systemd-homed paths under /var/home/... stay allowed. Also normalize POSIX
shapes at the source (_as_posix_path) so every downstream block probe is
shape-consistent (/etc/../home/user -> /home/user).
Co-authored-by: rodboev <rodboev@users.noreply.github.com>
## Release v0.51.234 — Release HB (stage-q4)
Two medium-risk backend/infra fixes. All gates green.
### Fixes
| PR | Author | Fix |
|----|--------|-----|
| #3289 | @rodboev | Refuse server startup when a live instance already serves the port (Windows/macOS silent port-sharing hazard). Live-listener probe (`GET /health`, 2s timeout) + Windows `SO_EXCLUSIVEADDRUSE` — **preserves fast restart** (POSIX keeps `allow_reuse_address=True`; a dying socket in the kernel backlog times out → startup proceeds). |
| #3486 | @dso2ng | Allow remote/SSH terminal profiles to use target-side workspace paths under `terminal.cwd` without a server-local `stat()`. Local profiles unchanged — bypass only fires for remote backends and only for paths contained within `terminal.cwd`. |
### History note on #3289
This PR was **held earlier this sweep** — its original form globally disabled `SO_REUSEADDR`, which a Codex gate flagged as breaking fast restart (TIME_WAIT bricks rebind for ~60s). The contributor reworked it along the suggested lines (live-listener probe instead of the global disable). This release ships the reworked version. Unheld → full pickup → full gate.
### Gate results
- **Full pytest suite**: 7458 passed, 8 skipped, 3 xpassed, **0 failed**
- **ruff forward gate**: CLEAN
- **browser-smoke gate**: CLEAN (real server boots fine with the new startup probe)
- **Codex (regression)**: SAFE TO SHIP (verified fast-rebind preserved + remote bypass gated on backend+containment, local validation unchanged)
- **Opus (correctness + security)**: SAFE TO SHIP (probe false-positive, `_is_within` containment, local-profile bypass all hold up; applied its one minor double-call cleanup note)
Closes#3289.
Co-authored-by: rodboev <rodboev@users.noreply.github.com>
Co-authored-by: dso2ng <dso2ng@users.noreply.github.com>
