fix(git,macos,runs): close the review findings on #22, #34 and #38

- validateRemoteUrl checks the literal scheme prefix git will receive and
  refuses %/backslash in the authority (WHATWG normalises https:/host and
  percent-escapes that git reads differently); route test for EBADURL.
- Parent-session scrub also drops AI_AGENT, and GIT_EDITOR when it is
  Claude Code's `true`.
- canonicalCwd resolves a not-yet-existing path through its deepest
  existing ancestor, so a symlinked parent still yields one lane.
- Note the clock-step ceiling on liveServers' boot-time filter.
- Docs/header wording: the Active runs count is lane-scoped.

docs/LANES.md

@@ -22,7 +22,7 @@ agenthub lanes add --cwd /path/to/repo --title "My Feature"
 
 The lane is now ready to track work. When you run a Claude Code session in that directory (or a subdirectory), the dashboard will bind the session to the lane automatically by matching the cwd.
 
-**Note:** The directory must exist and be an absolute path. A lane with a cwd of `/tmp/wt` will NOT capture `/tmp/wt-sibling` (no partial prefix match) but WILL capture sessions in `/tmp/wt/subdir/` (subdirectories are owned by the parent lane unless a deeper lane exists). A `cwd` that exists is stored by its real path (`fs.realpathSync.native`), so `/tmp/wt` on macOS is stored as `/private/tmp/wt` and a differently-cased path on a case-insensitive volume as the spelling on disk — the path a session reports. A path that does not exist yet keeps the string it was given; rows created before this rule keep theirs.
+**Note:** The directory must exist and be an absolute path. A lane with a cwd of `/tmp/wt` will NOT capture `/tmp/wt-sibling` (no partial prefix match) but WILL capture sessions in `/tmp/wt/subdir/` (subdirectories are owned by the parent lane unless a deeper lane exists). A `cwd` that exists is stored by its real path (`fs.realpathSync.native`), so `/tmp/wt` on macOS is stored as `/private/tmp/wt` and a differently-cased path on a case-insensitive volume as the spelling on disk — the path a session reports. A path that does not exist yet is resolved through its deepest existing ancestor (`/tmp/new` → `/private/tmp/new`); rows created before this rule keep theirs.
 
 To provision a dashboard-managed git worktree instead of adopting an existing directory, use a source repository:
 
@@ -438,7 +438,7 @@ The **Active runs** button in the console header opens the merged run list. It s
 
 1. live in-memory tmux runs from `GET /api/run`,
 2. persisted dashboard runs from `GET /api/run/history`,
-3. Claude Code sessions running **outside** the dashboard — `GET /api/sessions?status=active`, i.e. a `claude` the user started by hand in a terminal tab. These carry an amber `external` badge, and the button's live count includes them, so two hand-started agents read as "2 active runs".
+3. Claude Code sessions running **outside** the dashboard — `GET /api/sessions?status=active`, i.e. a `claude` the user started by hand in a terminal tab. These carry an amber `external` badge, and the button's live count includes the ones its lane owns (next paragraph), so two hand-started agents in the lane's folder read as "2 active runs".
 
 An external session is deduped against a dashboard run with the same `session_id`, and sessions from a remote data source (`source !== "local"`) or without a `cwd` are skipped — neither can be resumed on this machine.