Fix semantic drag selection over-running non-word ranges into the next word

[warp-dev-github-integration]

Human Remarks (Andy)

double-click-and-drag works differently in the block list vs rich text views and the block list behavior is the correct one. This PR resolves that difference and makes rich text behave the same. Added some more tests for this case.

Description

Semantic (double-click) + drag selection in agent conversations over-extended: when the drag tail landed on a non-word character (e.g. , or ...), the selection jumped to the end of the next word instead of stopping at the end of the non-word run. The terminal block list already behaved correctly.

Root cause: rich-text semantic expansion used word-boundary iterators that start outside a word — word_ends_from_offset_exclusive (forward) and word_starts_backward_from_offset_exclusive (backward) in crates/warpui_core/src/text/word_boundaries.rs. When the tail sits on a boundary char, the iterator skips the whole boundary run and continues into the adjacent word. The buggy pattern was duplicated in two call sites: FormattedTextElement::expand_selection (the AI/agent/markdown/code-block path) and Text::expand_selection (plain Text, e.g. table cells). The terminal block list uses a separate, correct path (grid handler semantic_search_left/right) that stops at the first boundary char.

Fix: add a shared TextBuffer::semantic_expansion_target(position, direction, policy) that snaps to the maximal contiguous run of the same character class as the char under the tail:

• tail on a word char → end/start of that word (unchanged);
• tail on a non-word char → end (forward) / start (backward) of the contiguous boundary run, never crossing into the adjacent word.

Both expand_selection call sites now route through this helper (kept in sync), and word_boundaries::is_word_boundary is exposed for reuse. The terminal block list is unaffected (separate path).

Intended behavior change: double-clicking directly on punctuation now selects the punctuation run rather than prevWord punct nextWord, consistent with the grid.

Linked Issue

Reported via the factory-client bug-triage Slack thread (linked below).

• The linked issue is labeled ready-to-spec or ready-to-implement.
• Where appropriate, screenshots or a short video of the implementation are included below.

Testing

• Added regression unit test crates/warpui_core/src/text/word_boundaries_tests.rs::test_semantic_expansion_stops_at_boundary_run (fails before / passes after): for foo... bar baz, forward target from offsets 3/4/5 == col 7 and backward from 3/4/5 == col 3 (buggy values were 10 and 0); word-char cases unchanged.

• ./script/format clean; cargo clippy --workspace --all-targets --all-features --tests -- -D warnings clean; full warpui_core test suite passes (293 tests).

• Manual UI verification on the running app (agent conversation): double-click foo, drag onto ... → highlights foo... (no longer foo... bar); double-click alpha, drag onto the comma → alpha, (no longer alpha, bravo); dragging onto a word still selects the whole word (alpha, bravo).

• I have manually tested my changes locally

Screenshots / Videos

Verified on the agent-conversation surface (screenshot posted in the Slack thread).

Agent Mode

• Warp Agent Mode - This PR was created via Warp's AI Agent Mode

---

Slack thread: https://warpdev.slack.com/archives/C0BCE7AELJ2/p1782281505938299?thread_ts=1782281505.938299&cid=C0BCE7AELJ2
Conversation: https://staging.warp.dev/conversation/a72ed78e-011f-4eb4-9072-e7dede99c407
Run: https://oz.staging.warp.dev/runs/019ef841-92c2-739f-bb00-7e91a9dd20eb

This PR was generated with Oz.

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@acarl005

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Overview

This PR routes semantic drag expansion for formatted and plain rich text through a shared helper so boundary-character tails stop before the next word, and adds unit coverage for non-word tails. I found no diff-line code correctness, security, or spec-context issues in the provided artifacts.

Concerns

• This is a user-facing selection behavior change, but the PR context only says a screenshot was posted in Slack; no screenshot or screen recording is attached or embedded in the PR description. For this user-facing change, please include screenshots or a screen recording demonstrating it working end to end.

Verdict

Found: 0 critical, 1 important, 0 suggestions

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