fix(solid_generator): qualify cross-file registry entries by origin library

[nank1ro]

Closes #110. Extends the unreleased 3.0.0-dev.5 (no version bump — tag after merge, per plan).

Problem

The cross-file registry is keyed by simple class name, so a local plain Foo and a foreign @SolidState-bearing Foo were mutually exclusive: registering the foreign one wrongly rewrote the local class (caught in #109's review), and blocking registration — the shipped trade-off — silently lost the genuinely reactive foreign read.

Fix

• Entries under a shadowed or multi-origin name are recorded qualified by origin library (name → originUri → fields side-maps). The flat registry is stripped for flagged names, so every other consumer sees byte-identical behavior for the unflagged common case.
• The value rewriter resolves a flagged name only when the receiver's tier-1 resolved staticType library matches a recorded origin (asset:<pkg>/source/... normalized to the registry's package:<pkg>/... — verified against package:build's AssetId internals, and it's the build convention build.yaml mandates for every consumer, not a repo-local accident).
• Conservative invariant: AST-only receivers (tiers 2–4 carry no library) never rewrite an ambiguous name — the change can only add rewrites proven by real resolution, never introduce a wrong one. Pinned by a red/green-by-construction unit test.

Review guide

Artifact	Proves
cross_file_qualified_registry_disambiguation (new)	two distinct @SolidState Foos in different files, consumed in one file — each read lowers against its own class (reviewer-probed at N=3 too)
cross_file_super_param_one_hop_local_shadow (updated)	the #109 trade-off resolved: thing.label (foreign, reactive) now lowers; f.label (local, plain) stays untouched
cross_file_local_shadowing_decoy (comment-only)	output byte-identical — but the mechanism verifiably moved from registration-blocking to tier-1 URI mismatch
value_rewriter_test.dart addition	AST-only receiver + matching origin still refuses (cannot pass for the wrong reason)

Deliberate side-effect (changelogged): dispose auto-injection no longer recognizes a 2+-origin name as @Solid-annotated (previously it fired non-deterministically for whichever origin registered first) — pass dispose: explicitly for such same-named classes.

Verification

352/352 solid_generator tests (goldens + idempotency ×2), 11/11 integration, repo-root dart analyze --fatal-infos zero, format clean, 5 example apps zero-delta. Pre-release validation against fairtile via path overrides: byte-identical app output, the #108 bare-super.x probe lowers, and a live local-shadow probe (plain local AuthRepository beside the real reactive one) disambiguates correctly in the real app — tree left clean.