[tiensonqin]

Summary

Keep the full visible glyph advance when a shaped line ends in U+200B and the trailing anchor shares a cluster with visible text. Caret positions, hit testing and selection now use the same fraction. Ordinary clusters and existing RTL inversion are unchanged.

Four internal text files only; the sidebar measure-cache fix is not included.

Testing

• Go 1.27.3, CGO_ENABLED=0: the single synthetic shared-cluster regression failed before the fix and passes after it; targeted internal/text and ui tests pass.
• Darwin/arm64, Linux/amd64 and Windows/amd64 normal + production builds/vet pass. Filtered WASM vet/build passes; build excludes the CLI and packages containing only tests.
• Full go test ./... fails only TestLocales (x-Test versus en-001) on BOTH this branch and clean fca5c736; no suppression or preference changes.
• A separate combined Logseq candidate passed one bounded real MyGo/native-worker caret trial. This is integration evidence, not exhaustive platform-shaping or RTL runtime coverage.
• Release counter size: macOS unchanged; Linux +4,096 B; Windows +1,536 B. hello is byte-identical on all three targets. Linker -dumpdep, symbol and section comparisons attribute growth to shared native text-layout/Line metadata and ELF/PE alignment; no new opt-in dependency or callable-symbol reachability.
• Formatting and diff checks pass. No dependency/compiler repin.

Tested on:

• macOS
• Windows — cross-build/vet only
• Linux — cross-build/vet only
• Web — filtered WASM build/vet only
• Other: none

AI disclosure

• Tool and model: Devin by Cognition AI; the underlying model/version is not exposed by this session.
• Used for: implementation, the regression case, review, validation and this description.
• A human read every line of this change and can explain it.

Link to Devin session: https://app.devin.ai/sessions/949a417dd06241acb1e04361de5b162b
Open in Devin Desktop: https://app.devin.ai/desktop/session/949a417dd06241acb1e04361de5b162b?variant=devin
Requested by: @tiensonqin

[devin-ai-integration]

I'll fix CI failures and address comments from users with write access. I'll skip comments containing "(aside)".

• Disable automatic comment, CI, and merge conflict monitoring