Eight unresolved doc references and broken README-rewritten links
that surfaced under `dart doc --validate-links`:
- Library-scope refs `[spawn]`, `[openProject]` qualified to
`[Backend.spawn]` / `[Backend.openProject]`; same treatment for
`[resolvePaths]` / `[applyResolved]` on Toolchain.
- `[D-41]` was a decision ID, not a Dart symbol — drop the brackets.
- `[from]` from I18n.interpolated qualified to `[I18nReplacer.from]`.
- `[DefaultSurfaceMap]` was a stale name (private `_defaultSurfaceMap`
in resolver.dart); switch to backticked path reference since
dartdoc can't link private members.
- `[icons/]` was a directory, not a symbol; backticked path.
- README links to `legacy/`, `docs/initial-plan.md`, `decisions/`,
`LICENSE` rewritten as absolute github.com/postmeridiem/clide URLs
so dartdoc stops re-rooting them into the doc tree.
Co-Authored-By: Claude <noreply@anthropic.com>