fix: seat the build stamp in #120's redesigned bar, and stop it faking a ticket id

Three things the merge with #120 (ui/shell-polish) actually required, none of
which a clean auto-merge could have told us.

MOVED, not preserved. #120 left <header>'s markup alone but gave every child
explicit styling and a stated reading order -- "what this is, which document,
which view, which mode, what keys, what the peer is doing". A build identifier
is "what this is", so the span moves from after #status to beside <h1>. Keeping
it at the tail was loyalty to my own first draft: it read as metadata trailing
#status, and with #hint's `flex: 1 1 auto` fighting for the slack a 40-char
commit SHA there is the thing that crowds the bar.

STYLED, because unstyled is illegible-by-default in a design system. It takes
`var(--dim)` -- the same token #hint and #status use, so it tracks both themes
by construction rather than by a hand-picked colour -- at 0.72rem, and clamps
to 14ch. Measured under Chromium on the merged tree: a tag renders whole
(scrollWidth == clientWidth, 69px), a 40-char SHA truncates to a 13-character
prefix with an ellipsis, and `header` does not overflow in either case
(scrollWidth == clientWidth == 1280). Contrast of rgb(107,103,95) on
rgb(244,241,234) is ~5.0:1, above AA for small text. Selecting the text still
copies the whole SHA -- text-overflow is a rendering clamp, not a truncation.

NOT AN ID. `improvise-web.tar.gz` puts the token `improvise-web` in the tree,
and AGENTS.md's audit matches `improvise-[a-z0-9]{3,8}` -- so the artifact name
resolved to no ticket and read exactly like a dead id, which AGENTS.md calls
worse than one. `improvise-installer.sh` escapes only by being ten characters,
which is luck rather than a rule, so the exclusion list gains `web` and the
paragraph gains the general case.

RELEASING.md (which arrived in this same merge, from improvise-gx5d) listed
what a tag publishes and was made wrong by omission; it now names the web
capture and says plainly that it is not what Pages is serving.

Verified on the merged tree: 1631 cargo tests over 37 binaries, node --test
47 -> 50 (so #120's three new shell tests survived the merge rather than being
silently dropped), 42 Playwright tests green under Chromium, and the stamp
gate re-proved by injecting the missed substitution again -- a header rewrite
does not carry the old fault injection.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FC2jVn8Au7E9JPkw6bwXXH

RELEASING.md

@@ -48,7 +48,19 @@ moved. Every step below exists to put that check before the irreversible one.
 
 5. **Watch the run.** A green release takes about three minutes and publishes
    tarballs for all four targets with their `.sha256` files, `sha256.sum`,
-   `dist-manifest.json`, `source.tar.gz` and `improvise-installer.sh`.
+   `dist-manifest.json`, `source.tar.gz`, `improvise-installer.sh` and
+   `improvise-web.tar.gz` — the assembled landing page and browser app, stamped
+   with the tag, which the page then shows in its header (improvise-oujb).
+
+   **`improvise-web.tar.gz` is a self-hostable copy and a rollback target, not
+   what the published site is serving.** GitHub Pages tracks `main` and a tag
+   does not deploy it, so the site and the release are deliberately different
+   code. Two things follow when the web half goes wrong. `release.yml` is
+   autogenerated, so never hand-edit it: change `dist-workspace.toml` and re-run
+   `dist generate`, which should leave the workflow byte-identical. And a
+   **pull-request** run of the Release workflow skips `build-global-artifacts`,
+   so a green PR says nothing about the web capture — to exercise it without
+   cutting a tag, run `dist build --artifacts=global` locally.
 
    The failure signature is unmistakable once you know it: **`plan` fails in
    about twenty seconds and the four jobs behind it skip.** That is the tag not