[jonaraphael]

Column resize handles swallowed small blank cells and had a dead strip on fractional gridlines: clicking the line could select cells instead of resizing. Multiline automatic widths also counted entire strings, and manual width overrides did not survive closing the editor.

Resize hover, drag and double-click now share one painted-boundary check. The grab band is at most 4 CSS pixels per side and shrinks to a quarter of the visible width for narrow cells. Exact and fractional collapsed borders work from either side, including row/table event targets and partially covered frozen seams. Cell centers remain selectable and editable; links, controls and active text edits retain their normal interactions. Hit testing uses a bounded number of paint probes rather than scanning rendered cells.

Manual sizes use border-box dimensions so the column follows the pointer without adding padding twice. Reset restores the original width and box-sizing CSS. Automatic widths use the longest physical line, and manual overrides persist per file and apply to later chunks. README describes the behavior. No new settings or commands.

Addresses #87, #98 and #101. Depends on #111 and #109.

Validation:

• npm test: compile and 167 tests pass, including narrow-cell center editing, exact/fractional borders, row/table targets, header-off previous-column ownership, frozen/partially covered seams, controls, bounded hit testing, persisted/chunk widths and box-sizing reset.
• npm run lint: zero errors and 87 existing warnings; git diff --check passes. Independent source review and focused tests cleared the changes.
• Final combined review build: compile and all 434 tests pass; lint has zero errors and 86 existing warnings. Existing keyboard, clipboard and editor-switch regressions remain covered.
• Actual Chromium pointer checks reproduce both reported failures before the fix and pass afterward: a newly inserted17px column selects, double-clicks, accepts text and posts its edit; the previously failing rounded x110 border drag now resizes only the correct column. Header-off right-side dragging and double-click reset pass.
• Measured drag+40 changes actual width59.148px to99px (under0.2px rounding), rather than116px before the correction. After horizontal scrolling, a frozen-seam drag changes only the frozen column17px to57px and leaves the occluded source column untouched.
• Browser checks use synthetic provider-generated HTML and the actual integration scripts; no native VS Code resize smoke is claimed.