Add virtual data bindings

[titouanmathis]

Summary

• add virtual data-bind:* attributes to apply one Data value to multiple DOM targets
• support property, attribute, class, style, and text bindings with value, target, and $data expressions
• preserve element content by replacing the legacy single-property write when virtual bindings are present
• handle HTML property-name casing, boolean/removal semantics, expression isolation, and equal-value dispatch
• document the API with a Tabs-like Action/Data example

This is a stacked follow-up to #511 and should be reviewed against feature/data-scope. Once #511 merges, this PR can be retargeted to main.

Validation

• npm run test — 47 files passed, 310 tests passed, 3 skipped, 1 todo
• npm run lint:types — passed
• npm run lint:static — passed with 15 pre-existing warnings and no errors
• npm run lint:prettier — passed
• npm run build — passed

No local docs build was run.

Part of #510.
Depends on #511.

[github-actions]

Code Review

Risk: Low — no blocking issues; safe to merge aside from nits.

This MR adds virtual data-bind:* bindings so one data value can drive multiple DOM updates on the same element, and documents the new API with a Tabs-style example. It also adds tests for property-name resolution, attribute/class/style semantics, scoped expressions, and equal-value dispatch.

Still open from earlier reviews (1 finding):

• packages/ui/Data/DataBind.ts:22 — issue: Acronym-cased DOM properties are mapped incorrectly

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Review usage: 209,237 in (155,136 cached) / 8,180 out tokens — $0.2967 (cloudflare-ai-gateway/gpt-5.4, thinking: medium)

Reviewed by @weareikko/code-review v0.8.2 for commit b798bb1.

Previous review runs

Previous run archived 2026-07-15T15:17:27Z

Code Review

Risk: Medium — issues that should be addressed before merge.

This MR adds virtual data-bind:* bindings to DataBind, updates dispatch semantics so virtual subscribers still refresh on equal-value updates, and documents the new API with a Tabs-like example. The implementation and tests cover property, attribute, class, style, and text bindings, plus scoped $data expressions and per-binding error isolation.

1 issue found:

• issue — packages/ui/Data/DataBind.ts:22 — Acronym-cased DOM properties are mapped incorrectly

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Review usage: 66,015 in (44,544 cached) / 7,495 out tokens — $0.1772 (cloudflare-ai-gateway/gpt-5.4, thinking: medium)

Reviewed by @weareikko/code-review v0.8.2 for commit 7f2fe4f.

[codecov]

Codecov Report

❌ Patch coverage is 98.18182% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 78.70%. Comparing base (7d58c48) to head (b798bb1).

Files with missing lines	Patch %	Lines
packages/ui/Data/DataBind.ts	98.18%	1 Missing ⚠️

Additional details and impacted files

@@                   Coverage Diff                    @@
##             feature/data-scope     #513      +/-   ##
========================================================
- Coverage                 79.45%   78.70%   -0.75%     
  Complexity                  145      145              
========================================================
  Files                       100       94       -6     
  Lines                      3008     2874     -134     
  Branches                    532      502      -30     
========================================================
- Hits                       2390     2262     -128     
+ Misses                      542      536       -6     
  Partials                     76       76              

Flag	Coverage Δ
unittests	78.70% <98.18%> (-0.75%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
packages/ui/Data/DataBind.ts	98.25% <98.18%> (-0.05%)	⬇️

... and 13 files with indirect coverage changes

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