SD-2447 - fix: tab stop computation and alignment for TOC styles

[chittolinag]

Issue

• computeTabStops() stopped seeding the default 0.5″ grid whenever any explicit tab existed, so TOC paragraphs (which only declare a right-aligned dot-leader tab) lost their left-aligned defaults and the first \t jumped straight to the leader. Even after the grid was restored, the DOM measurer and layout remeasurement consumed the first explicit stop for every tab, so the final TOC tab often targeted a default stop instead of the right-aligned one—especially when the PAGEREF tab remained embedded inside a text run.

Proposed solution

1. computeTabStops() now seeds the 0.5″ default grid from 0 twips whenever a paragraph lacks start-aligned explicit stops (TOC scenario), but retains the original behavior for paragraphs that already define their own left tabs so existing documents aren’t disturbed.
2. Both the DOM measurer and layout-bridge remeasurement expand literal tab characters into TabRuns, track the total tab count, and map the last N tabs to the N explicit right/center/decimal stops. That keeps the trailing TOC tab pointed at the right-aligned stop (and renders the leader) even when earlier default stops exist.

Note

This PR depends on SD-2440.

[linear]

SD-2447 BUG: TOC renders with incorrect formatting after document loads

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Count inline tab characters when mapping alignment stops

applyTabLayoutToLines() now maps the last tab ordinals to explicit end/center/decimal stops, but totalTabRuns only counts runs with kind === 'tab'. In paragraphs where a tab remains embedded in a text run (the TOC/PAGEREF case this commit targets), consumeTabOrdinal() still advances for "\t" characters, so later ordinals are treated as out-of-range and the explicit right-aligned stop is applied to the wrong tab (or not applied at all). This leaves remeasurement output inconsistent with the DOM measurer and keeps TOC page-number alignment incorrect for mixed tab-run/text-tab input.

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