v0.1.15: fix network over MCP, stable request ids, sharper tool docs

0.1.15: fix network over MCP, stable request ids, sharper tool docs

Glama scored the v0.1.14 tool set B 3.4/5; outline was the only C (2.9)
and the server score weights the minimum tool at 40%, so this release
rewrites the terse descriptions and fixes the two real bugs they exposed.

• network_detail ran response.text() from the MCP handler thread: every
  call over MCP raised a greenlet error. It now goes through on_page like
  every other browser operation.
• network entries carried live Playwright request/response objects, so the
  MCP layer's json.dumps crashed. network_tail projects serializable
  fields and adds an id; network_detail looks the request up by that id
  (a ring-buffer position shifts once 200 entries are recorded).
• the id counter is shared across tabs, a tab's recorder is reused when it
  is selected again (no double listeners, history kept), and closed tabs
  are pruned.
• fill_form check accepts the true-like strings a model sends; outline,
  console, goto, network, network_detail, fill_form and press_key now
  document what they actually return and change.
• tests: 220 (id round-trip over MCP, ring overflow, tab recorder reuse,
  check values, network json path).

Reviewed by oc-review over three passes (final pass only style nits).