Covers the rail: one fixed width across tabs, no rail without a project, the browser tab withheld where no browser exists, the pinned loop verdict surviving tab switches, the History naming and tooltips, tabs earned by content (empty reads drop tabs, nothing at all drops the rail, pending first reads do not blink, a lost tab falls back), and the launcher owning docs/history withholding those tabs and skipping their reads.

## Before writing SPEC.md files

Read https://raw.githubusercontent.com/brillout/sdd/refs/heads/main/sdd.md
