Remove duplicated code across the app, libraries and adapters #528

Part of #494.

Problem

A duplicate-block scan over every package's source (8 consecutive normalized lines repeated across or within files) found 33 duplicated blocks. Duplicates have to change together, and CLAUDE.md asks for one source of truth per concept, with logic shared by adapters in core.

Scope

Each finding is either consolidated in the package the import rules allow, or kept with the reason stated in its PR:

• App styling and tooling: a second full Tailwind build in every component's styles, a Tailwind v3 config v4 never reads, a duplicate --spacing, autoprefixer (which added only -o-object-fit), and repeated component CSS and handlers.
• Library packages: page-script naming steps, the UiAutomator driver check, the Nightwatch config file names, and repeated conformance allowlist rules.
• Adapters: screencast lifecycle logging and BiDi sink wiring repeated across adapters (moved to core), plus repeats inside single adapters.

Kept on purpose: the light and dark theme values in colors.css, each component's own Lit context declarations, @wdio/elements' explicit export list (the gate on that published API), and type re-exports under stable local names.