probbit monitor: watch an individual's inner state live

[BitmapAsset]

probbit monitor: watch an individual's inner state live, inside the probbit binary, with no dependencies: as bars in the
terminal, or as a page in the browser served from 127.0.0.1.

It replays a strand (the header holds the persona, the initial state and the engine version; one line per event holds the
inputs) with the rules of probbit live verify, recomputing every stance document from the strand alone, so it works for any
strand on any machine and needs no extra log. It says "replay verified" when the chain checks, and names the line when one
differs. It changes no file (the demo's week goes through a temporary one, removed at once) and sends nothing anywhere.

Done against the done-when list below, CI green on ubuntu, macOS, Windows and wasm at the head; a draft until it is reviewed.

• A. Subcommand: probbit monitor STRAND [--follow] [--once] [--plain] [--fps N] [--serve] [--open] [--port N] and
  probbit monitor --demo [--once] [--plain] [--serve] [--open] [--port N] (--open serves the page as --serve does and
  starts the browser), with help in the style of the other subcommands
  and exit codes 0 (every line replays), 1 (a line differs: named in the frame, which shows the event before it), 2 (a bad
  flag, a port that cannot be had, an unreadable file, a file that is not a strand). Terminal view: one row per trait (its
  levels as segments with their odds, the level taken highlighted, its phrase), moods with a sparkline of the last 50 events,
  senses (flags, levels, numbers, the clock, history features), habits (bound ones marked, the violations counter), learned
  deltas as centred bars within the cap, drives rows when a document carries pursue / drives (feature-detected), the stance
  line and why. --plain is plain ASCII; colour follows the existing theme rules (NO_COLOR, PROBBIT_THEME=plain,
  TERM=dumb).
• B. Replay engine shared with live verify: done. live::Replay (open the header, step one line, summary); verify is a
  loop over it, and the existing live tests pass unchanged. Unit tests replay strands of the three example personas (each
  one's scripted --demo week, seed 2, and a strand that lights every input in turn) and check each monitor document's sha256
  against the line's stance digest, on every line, and that the replay ends where verify does. --follow draws an
  appended line within a second (tested), replays a truncated strand from the start with a warning, waits out a removed one
  and follows a rotated one (tested).
• C. Server: done. --serve binds 127.0.0.1 with std TcpListener and no other address (there is no host flag; --host
  / --bind exit 2 saying so), port 0 by default (a free one) or --port N; the URL is the line on stdout. It answers GET
  requests addressed to 127.0.0.1:PORT or localhost:PORT (others get 403, so a page of another site that resolves its name
  to 127.0.0.1 cannot read the documents): / the page (one file embedded in the binary, 21 KB, styles and script inline,
  a Content-Security-Policy that lets it connect to nothing but its own server), /events server-sent events (the layout,
  the latest frame, then a frame per event; a heartbeat comment after 15 quiet seconds; events that land within one 100 ms
  poll, or while a page falls behind, come as the latest frame), /doc/N event N's stance document as
  probbit live printed it (the latest 10,000 kept). The strand is followed with the same replay as --follow; while a
  long strand replays from its header (10,000 events: about 3.5 s), the page and the terminal draw the board every 250 ms
  with a note. --open starts the default browser (BROWSER, else open / cmd /c start / xdg-open), best effort: a
  browser that does not start fails nothing. A thread per connection, at most 64 at once. Nothing beyond std, so the same code
  on macOS, Linux and Windows; the server tests run in the existing CI matrix.
• D. Demo mode: --demo in the terminal (paced at a terminal; --demo --plain --once deterministic and tested) and
  probbit monitor --demo --open (or --serve without the browser), the week paced 1 s per hour and each night in 2 s,
  over and over, for the page (a week that starts over goes from its last event straight to event 1; the night's note sits
  in the header row, so the board holds still).
• E. Tests: tests/monitor.rs: help; a --once --plain frame pinned byte for byte on the tutor's demo week (the last
  event and a failure turn); exit codes; --follow pickup, truncation, removal, rotation; and the server: GET / (the page,
  under 40 KB, no URL in it but the SVG namespace), /doc/1..3 equal to probbit live's stdout lines byte for byte, 404s,
  the host guard (403), /events (the layout, then the latest frame with that document; a line appended to the strand is
  pushed as the next frame and /doc/4 serves it), a port in use (exit 2), --open with a browser that does not start
  (the server runs on), --demo --open serving the demo's page and stream, and the flag errors (7 tests). Unit tests (9):
  replay equals verify on the three personas' scripted weeks and on strands that light every input, plus any strands named
  in PROBBIT_MONITOR_STRANDS (a copy of a real 14-event strand passes); a hand-written document with drives / pursue
  draws its rows, and passes through to the page's frames as it is (the page draws it too, checked in headless Chrome: no
  script error); a long replay is published on the way; the event stream's heartbeat (a 100 ms beat in the test); the page's
  layout follows the persona's order; the embedded tutor equals the example; cell rounding.
• F. Docs and assets: CHANGELOG lines under 0.8.0 (unreleased); docs/persona.md §5.8 (the board, the terminal flags, the
  --serve routes and frame fields, the host guard, the demo, exit codes) and its row in the command table; README "Watch it
  live" right after "Live" (three lines, probbit monitor --demo --open, the GIF) and the documentation map; the cheat
  sheet's monitor rows and exit codes; docs/agents.md (a person can watch the individual behind a strand_path).
  docs/probbit-monitor.gif: the tutor's week in the browser, 1280x720, 14.9 s, 1,895,852 bytes (headless Chrome screenshots
  of --demo --serve every 400 ms, assembled with ffmpeg at 10 frames/s, a 128-colour palette); docs/probbit-monitor.png:
  the page at event 21, a failure turn (no_jokes_on_loss bound, humour none 1.00).
• G. Gates: cargo test --release --workspace green locally (macOS arm64, 54a1794: every suite, probbit-decide's
  acceptance 19/19; that crate is unchanged, and its wall-clock asserts need its CI threshold on a machine at load 50+);
  clippy: 0 new warnings; no new dependencies (Cargo.lock unchanged); release binary 2,317,328 bytes vs 2,190,320 on main,
  +127,008 bytes (macOS arm64). CI at 54a1794: green on every job (tests on ubuntu, macOS and Windows, wasm, the four
  release targets).

main.rs changes are one module, one match arm and one usage line.