refactor(ui): wire the dimension classes to their tokens, and guard the token files

[renefloor]

Third in the stack: #182 → #183 → this. Base is chore/prune-unused-tokens, so the diff is only the wiring.

Why this exists

StreamSpacing, StreamRadius and the line-height scale hard-coded the same numbers the vendored token files already held. The design system's dimensions were mirrored twice, with nothing tying the copies together — the swatch-versus-baked-hex hazard one layer up, where an upstream change gets applied to one and not the other in silence.

An earlier revision of #183 deleted those unread constants instead. That removed the evidence of the gap rather than the gap, which is why they came back here and got wired.

What changed

StreamSpacing, StreamRadius, StreamLineHeight, StreamFontSize and StreamFontWeight now read their tokens. All values are bit-identical to the literals they replace — verified by resolving every expression and comparing IEEE-754 representations, not just ==. No golden moves.

New internal/tokens/stream_tokens_dimensions.dart sits beside the per-mode color files rather than under light//dark/, because the token repo publishes one set of dimensions for every mode — all 180 constants were byte-identical between the two files. Typed double so they satisfy Radius, EdgeInsets and TextStyle directly.

Font sizes mirror upstream's flavor split. iOS runs a size up at almost every step, so the token repo publishes a separate set and StreamFontSize ships two scales. Both are vendored, in internal/tokens/{android,ios}/stream_tokens_font_size.dart, keeping the bare upstream names. Everything else — spacing, radius, line heights, weights — is identical across android, ios and web and lives in the one shared file.

Weights are declared as FontWeight, not the raw 400/500/600/700. The vendored constants are already expressed in the types Flutter consumes rather than the types upstream emits — that is why the rest are double — and FontWeight has no public constructor from a number, so an int here could not be read in a const expression.

One upstream dimension is deliberately not carried: radiusNone, since the analyzer's use_named_constants prefers Radius.zero over circular(0). The font family is not carried either — this package never sets one for text, and ships no text font, only the generated Stream Icons face.

Two corrections found in review

The first revision wired StreamTokensTypography, an internal class of 20 TextStyle constants that nothing in the repo read — not one Dart file, only prose — while the public, exported StreamLineHeight still hard-coded its values. Ten constants were being kept alive by a dead intermediary. That class is gone, and StreamLineHeight reads the three line-height tokens.

The second was this PR claiming font sizes and weights could not be wired at all. Both arguments rested on the idea that only the web flavor carries the Geist family "this package ships". It ships no text font and never sets fontFamily for text, so the flavor question was only ever about sizes — and those are vendored per flavor now, with the weights alongside them.

All 23 wired values are identical to the literals they replace.

The guard

scripts/check_tokens.dart, wired as melos run check:tokens next to check:barrels in the same CI step. It fails when a vendored constant is never referenced, and when light/ and dark/ disagree about which constants exist — the second because a field resolving from a constant in one mode but not the other silently falls back.

It earned its place while being written: it caught radiusNone having no reader, and a stale directory-wide skip that was hiding a file's reads.

It has since been hardened against passing vacuously. A guard that exits 0 because it found nothing to inspect is worse than no guard — it prints the same tick as a real pass. Review found five such paths, each reproduced by running the script:

scenario	was	now
both color files emptied	✓ 0 color tokens … all referenced	fails: minimum declaration count
dimensions file deleted	✓ … and 0 dimension tokens	fails: missing file
token directory moved	melos selects 0 packages, prints SUCCESS	fails: no package filter to miss
dead token mentioned in a doc comment	counted as a reference	fails: comments and strings stripped
a vendored file with no branch in the script	invisible	fails: uncovered-file check
a flavor file declaring names but imported nowhere	looked referenced	fails: per-file import check

Plus a declaration-count cross-check, so a form the pattern cannot parse fails loudly instead of becoming exempt; stale allowlist entries are reported; and the success line now names how many Dart files were scanned, so "nothing unreferenced" can be told apart from "nothing examined".

The melos entry no longer uses melos exec at all. Any package filter that stops matching selects zero packages and reports SUCCESS, so it runs once from the repo root and the script locates the package itself.

The allowlist is intentionally empty, and an entry matching no declaration is now a failure.

Verification

analyze clean across all four packages; format:verify, check:barrels and check:tokens pass. flutter test is +404 with the pre-existing 56 macOS-golden failures unchanged, so nothing rendered differently.

Both the guard's positive controls (dead constant, light/dark divergence) and all five hardened paths were confirmed by running the script against a deliberately broken tree and checking real exit codes.

✓ 163 color tokens, 27 dimension tokens and 8 font sizes per flavor, all referenced; light/ and dark/ and android/ and ios/ in agreement (209 Dart files scanned).

[coderabbitai]

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (chore/prune-unused-tokens@90d3b2e). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
...ternal/tokens/android/stream_tokens_font_size.dart	0.00%	1 Missing ⚠️
...s/internal/tokens/ios/stream_tokens_font_size.dart	0.00%	1 Missing ⚠️
...ives/internal/tokens/stream_tokens_dimensions.dart	0.00%	1 Missing ⚠️

❌ Your patch check has failed because the patch coverage (0.00%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@                     Coverage Diff                      @@
##             chore/prune-unused-tokens     #184   +/-   ##
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  Lines                                ?     8596           
  Branches                             ?        0           
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  Misses                               ?     2703           
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