fix(web): bound the SGR state and follow real terminal widths

Nine findings, one critical. Terminal cases verified in a real terminal first.

CRITICAL: cells held the accumulated SGR history, so every state boundary
re-emitted the whole chain — output switching color without a full reset
emitted O(n^2) characters. Measured: 3200 such cells produced 25 MB, and the
reviewer's ~90 KB alternating-color case is well under bash's own output cap.
State is now a normalized record (foreground, background, attribute set) with
one canonical sequence per boundary, so the emitted text is linear in cells;
the 90 KB case parses in 36 ms. That also makes the attribute closers every
chalk-based tool writes actually close: `\x1b[1mbold\x1b[22mplain` leaves the
following write PLAIN, which a real terminal confirms.

Width follows emoji presentation, not the U+2600-U+27BF block: `A✓B` redrawn
with `XY` shows `XYB`, so the check every progress line writes is ONE column.
Taking the block as wide misaligned exactly the output this card exists for.

Writing over either half of a wide pair blanks the other, since a terminal
cannot leave one cell of a two-cell glyph standing.

`line\n\x1b[0m` does not end in a newline as a string yet its last parsed line
holds nothing visible, so the terminator check now reads the parsed lines — it
had added a blank row and inflated the collapse count.

A line with no cursor movement no longer builds a column buffer at all; only
its SGR is folded, so an `ls -R` or a 5k-line log allocates nothing per
character.

The `.terminalDescription` rule had been inserted into an existing grouped
selector, silently giving `.codeBody` description typography and changing its
bottom margin from 4px to 0 — a pre-existing surface this PR does not own.
Split out, `.codeBody`'s margin restored.

Three comments contradicted their code: the fixture's exit-marker line (still
claiming recovery from a marker deliberately removed), `bash-sample`'s header
(still routing a click to the details panel, and calling the consumer's cap the
block's own), and a DetailsPanel comment stacked above the wrong rule. The
ui-primitives README documented only the CR/BS half of the replay, so a reader
would expect `OK0%` where `100%\r\x1b[KOK` renders `OK`.

packages/client/connection/src/client/fixture.ts

@@ -284,8 +284,10 @@ function buildAlphaLog(): SessionEvent[] {
   ]
   // Turn 65: the terminal sample turn 60's two clean prompt rows cannot cover —
   // ANSI SGR coloring, output past the terminal card's height cap, a nested cwd
-  // whose prompt label is its last segment, and a non-zero exit recovered from
-  // the trailing marker the bash tool appends. Named `bash`, so it also covers
+  // whose prompt label is its last segment, and a non-zero exit authored beside
+  // the sample in TERMINAL_EXIT_STATUS — its body deliberately carries no
+  // `[exit code: N]` marker, since the real presenter consumes that one out of
+  // the body. Named `bash`, so it also covers
   // the keyed toolview row (turn 60's `fx-bash` covers the render-site fallback
   // row) — the two chat-row shapes the terminal card renders in.
   //