Port the new UI design, and fix the load path it exposed

[IPerception]

Restyles the browser app to the design generated in Claude, while keeping every
feature added since that design was made. Both halves were the requirement: the
design was built from an early version and covers roughly half of what the app
now does.

Ships as v1.1.0.

Design

• 24 themed tokens across all four theme blocks. Light and dark are both the
  design's own values, recovered from the LIGHT/DARK maps in its script
  block — those tokens are applied at runtime and never written as CSS, which is
  why they first appeared undefined. The design re-tints toward blue on the
  way to dark rather than desaturating; deriving dark by preserving the light
  theme's neutral hue produced a flat charcoal that read visibly dull.
• The three identity hues the design has no colour for (shift, swap, deid)
  are generated at the measured lightness and chroma of its accent, per
  theme, so they sit at the same visual weight. New -2 variants take chip text
  on its own wash from ~3.8:1 to ~9:1 — AA rather than not.
• Barlow Condensed embedded, subset to the glyphs this app renders: 20.6 KB
  for both weights against 44 KB unsubsetted. web/embed-font.py is the tool.
  SIL OFL 1.1, no Reserved Font Name; the copyright, licence and URL ride in the
  font's own name table, because the single HTML file travels detached from this
  repo and a repo-only OFL.txt cannot discharge that.
• Every border-radius removed; the masthead moved into a full-width header
  carrying a mono readout strip; numbered rail stations; an accent rule under
  the selected tab; corner ticks on the four panels that do not repeat; and the
  graph-paper ground on the empty state only.
• Data rows get their own size lever, --step-row, separate from the chrome
  scale — Document, Tree, Claims and Checks read at 14px.

The grid ground is deliberately not on .stage. ROW_H is 24 and
TREE_ROW_H is 28 against a 28px grid: on the Tree that rules every row, and on
the Document the two pitches beat with a 168px period that crawls as a
virtualized list scrolls.

Fixes

• Loading a file left the previous document's view state in place.
  selectTab paints the row list before renderDocument rebuilds it, so a
  stale visible was indexed against the new document's segments and threw out
  of renderRow — aborting loadFile before renderDocument and
  updateReadouts. The file name changed, nothing else did, and no error
  reached the screen. The tree half of this reset always existed, which is why
  the Tree tab never had the bug.
• windowRange had no upper clamp, which is what made that silent: it
  returned first: 8325 against a total of 31, and the slice came back empty.
• The Document filter scrolled out of reach while the outline stayed pinned, and
  selecting a claim welded the list to the tab strip.
• .claims-scroll and the outline height cap were hand-tallied constants
  describing chrome that had changed height. Both now measure it.

Tests

• New render.mjs, a ninth suite. It drives the app against a thin DOM shim,
  including the load-over-load sequence the bug above lived in. Every other suite
  tests a pure function, and this class of fault was invisible to all of them and
  to every static check in lint.mjs. Verified by removing the state reset and
  watching the assertion go red.
• Two assertions that wrote down a number which was really a consequence of
  another number now derive it instead.
• lint.mjs rule 8 rewritten: the mask and theme toggles are asserted to sit in
  the page header rather than outside .rail-body, which no longer exists. The
  bug it guards has happened once, so it is re-expressed, not dropped.

Verification

node web/tests/all.mjs — all 9 suites green. python -m unittest — 11 tests,
green. The app is 290 KB, up from 256 KB; 20.6 KB of that is the embedded font.
Checked before staging that no design source material is committed: the
generated web/fonts/face.css is gitignored, and docs/notes/ — the artifact,
its 44 unpacked assets and 39 source .woff2 files — stays out.

Merging deploys to the live Pages demo, which tracks main rather than the tag.

🤖 Generated with Claude Code