v1.6.0: schema export and theming

Added

• Theming and custom palettes: match Truss to the app it is embedded in by defining your own colours and fonts from config under truss.theme. A small set of semantic knobs (accent, background, surface, text, border, and more) plus two font-family knobs re-skin the whole dashboard, chrome and diagram, in both light and dark; only the knobs you set are overridden, the rest stay on the default, so a handful of values is enough. Delivered as a same-origin stylesheet, so a strict Content-Security-Policy still needs only style-src 'self', with no build step and no extra request on a default install. Each value is validated before it is emitted, so an invalid value falls back to the default rather than breaking the sheet.
• Schema export from the command line: php artisan truss:export writes the database structure to DBML, JSON, CSV, a Markdown data dictionary, or Mermaid, for CI, tooling, and version control. The command-line counterpart to the dashboard export button, generated from PHP so it needs no browser. Writes to stdout by default (pipeable) or a file with --output, filters with --tables / --exclude (config excluded_tables always wins), targets a connection with --connection, and rebuilds first with --fresh. Output is deterministic (the same schema always produces the same bytes), so --check can fail the build when a committed export file has gone stale. Exit codes: 0 written or up to date, 1 --check found drift, 2 a usage or runtime error. Structure only, with no network call.

Removed

• The unused truss.diagram.theme config key (it was wired to nothing). Theme selection now lives under the new truss.theme block.

Fixed

• The dashboard toolbar no longer overflows the viewport on a small desktop. With every control active (filter, focus, depth, type labels, and the export, changes, health, legend, and theme buttons) and long table names, the bar could grow wider than the window; because it is sticky it pinned only vertically, so a horizontal drag slid the whole header sideways and clipped the brand. The secondary controls (focus, depth, type labels) now fold into the more menu below 1024px, the focus and connection selects are width capped, and the search field can shrink, so the toolbar always fits.
• On a phone the legend now opens as a top-right dropdown, matching the changes and health panels, instead of a full-width bottom sheet, so all the toolbar overlays behave consistently.