fix(files): the review's fixes for the Files panel delete

The fixes #529's review asked for, each with a test.

- No inline handler. The button quoted the path inside
  onclick="...decodeURIComponent('<path>')", and encodeURIComponent leaves
  ' alone, so a file named x'-alert(1)-'.txt ran script in Codeman's
  origin and it's.txt was a syntax error. It is now bound in the existing
  .file-tree-item loops from the row's escaped data-path.
- Symbolic links are refused, never followed. validateSessionFilePath()
  returns the realpath, so deleting AGENTS.md -> CLAUDE.md deleted
  CLAUDE.md and left the link dangling. The path as named is lstat'ed,
  a link answers 400, and the inode is compared again before the unlink.
- The edit route's confinement whole: validateLocalSessionFilePath()
  behind withGuardedOutsideWorktree(), so an absolute path in a followed
  outside worktree obeys the same rules, and the sensitive, blocked and
  .git checks run on both the realpath and the path as named.
- Adopted sessions are refused like remote ones (the /tmp exception of
  the older file surfaces is not copied to a new one); Docker workspaces
  are allowed, as on the edit route. The workspace is probed bounded
  first (#516). Errors are thrown with their status.
- Deleting from search results re-runs the search, the row buttons stay
  visible on touch screens, the confirm and toasts have zh-CN text, and
  no button is drawn for remote or adopted sessions.
- Docs: CLAUDE.md, architecture-invariants, api-reference and the
  Working With Files wiki page.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/wiki/Working-With-Files.md

@@ -19,6 +19,13 @@ not finish shows **Not fully scanned** rather than looking empty. A folder that
 such as a network mount that went away, is skipped rather than waited on and is marked the same way,
 so a search can miss what is inside it. The panel's Refresh button tries it again.
 
+Each file row has a download arrow and a × that deletes the file after you confirm. Both show
+when you point at the row, and always on a touch screen. Delete removes one file at a time,
+never a folder, and refuses a symbolic link (deleting one from here would remove the file it
+points to), anything under `.git`, and the sensitive files the viewer will not serve. It is not
+offered for remote (SSH) sessions or for tmux sessions opened from outside Codeman. Deleting
+from search results takes the row out of the results.
+
 It renders what it can:
 
 | Kind                     | Behaviour                                                                 |