v0.6.1 — the Stream earns its column

• Open the files the agents name. Every entry now wears the paths it
  named, and a click opens that file in the editor beside it — switching to
  the card's own worktree when it has one on this disk. Three sources, in
  descending order of trust: a commit's numstat keys (git's own answer), a
  created card's declared files, and what the prose names.
• The prose half is a guess and is kept one. Agents write paths to each
  other constantly — "the fix site is verbs/_facts.py::pending_mentions" —
  and no structured field carries them. So they are extracted, narrowly:
  backticked or bare, a trailing ::symbol / :line / :line:col stripped
  because events.py:53 names a file and not a file with that name, never a
  URL, never a bare directory, capped. A false negative costs a click; a false
  positive is the rail lying about the disk.
• Markdown, the drawer's own renderer over the same parser, so a fence, a
  list and a path read here exactly as they read there. The 96-character cut
  is gone: it landed inside a fence as often as not, and what the reader saw
  was not a shortened comment but a broken one. The clamp is now a HEIGHT,
  undone by expanding the entry — and expansion is a set, not a flag, because
  a reader opens two comments to compare them as often as one.
• The rail resizes by hand: a grip on its edge, 240–760px, double-click to
  reset, and the width is remembered across leaving the tab. The listeners are
  on the document and not the handle — bound to a 6px strip they are lost the
  first time the pointer outruns the render.
• useStream is the container half, extracted so a second mount of the same
  picture cannot come to disagree about what is new or which family is on.
• Four mutations, one site at a time. Two assertions were born FALSE and found
  by running them: a path cleaner that did not strip backticks, and a "draws
  no chips" claim asserted against a mount that HAD an editor.
• The bundle grew 341 411 → 345 368 bytes.