fix(pr-review-canvas): number full diff before filtering, fix ws-only check

[lab1207]

Fixes #472.

Two defects, one root pattern (mutating the diff before numbering it):

1. Import lines were deleted before line counters ran, so every line after a dropped import was numbered too low and import changes were invisible. Now the full raw diff is parsed and numbered first; imports collapse at render time into a visible "N import lines hidden" row (never silent), with a showImports opt-out on renderDiff.
2. isWhitespaceOnly stripped ALL whitespace, so "a b" to "ab" (and similar string/indentation changes) collapsed into unchanged context lines. It now collapses whitespace runs instead, so only true whitespace-only diffs merge.

Verified with a node harness against the issue's two reproductions: old code numbers const x as 1 and collapses the string change; fixed code numbers it 3/3 with a 3-import marker row, keeps the string change as del+add, still collapses pure-whitespace diffs, and renders everything numbered correctly with showImports.

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Note

Low Risk
Client-side diff rendering only; behavior is more accurate with backward-compatible renderDiff signature.

Overview
Fixes incorrect diff display in the PR review canvas by numbering and parsing the full raw patch before any filtering, instead of dropping import lines up front (which skewed line numbers and hid import edits).

Import handling moves to render time: hidden imports collapse into a visible "N import lines hidden" row, with optional renderDiff(..., { showImports: true }) to show them normally.

Whitespace-only merging is tightened: isWhitespaceOnly now normalizes whitespace runs rather than removing all spaces, so real content changes like "a b" → "ab" stay as del/add instead of folding into context. Whitespace merging runs in a second pass and can merge line-by-line within mixed del/add blocks (e.g. alongside import changes).

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[cursor]

Stale Bugbot comment from a previous run.

[lab1207]

Good catch - fixed in 57b1bc2. Replacement blocks now merge whitespace-only pairs independently instead of all-or-nothing, so an import edit in the same block no longer stops a formatting-only pair from merging (the import pair itself stays hidden behind the marker). Numbering is untouched - entries keep their parsed numbers either way. Verified with a node harness: the mixed block renders one context row plus markers, no add/del rows.

[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 1 potential issue.

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[cursor]

Partial merge splits paired lines

Medium Severity · Logic Bug

When a replacement block mixes whitespace-only pairs with real edits, leftover add rows are appended after later merged ctx lines. That separates a deletion from its matching addition and emits new-side line numbers out of order.

 

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