feat(solid_generator): track foreign signal reads

[nank1ro]

Reads of hand-written solidart signals (e.g. reached through @SolidEnvironment objects) now count as reactive dependencies, per SPEC §4.5/§5.1 — previously the reactivity analysis only counted generator-managed members, so a build() reading gate.complete.value got no SignalBuilder (silently non-reactive widget) and a @SolidState getter over a foreign signal was rejected with "has no reactive dependencies".

Found in production shape in fairtile_esg's pmi_app shell (Valutazione tab never appearing until a navigation-forced rebuild).

What's in here

• _maybeRecordForeignSignalRead in value_rewriter.dart: records reads of receivers statically typed as solidart SignalBase subtypes, for .value / hasValue / previousValue / hasPreviousValue / state and the callable form (sig(), handled in visitFunctionExpressionInvocation — the analyzer rewrites zero-arg signal calls there, never MethodInvocation). A dedicated foreign-only getter set keeps the shared managed-member sets untouched (a machine.state read on a @SolidState field still lowers to machine.value.state — regression-tested).
• Collision-proof key namespace (foreign: prefix, this.-stripped) so §7.5 wrap pruning can never conflate a foreign signal with a same-named managed member; symmetric offset guard.
• .untracked chains are honored as an opt-out for build() wrap placement.
• target_validator's resolved tier now uses isSolidartSignalType (solidart + flutter_solidart): the SPEC §3.6 rejection of @SolidEnvironment on SignalBase-typed fields previously could not fire in any real resolved build (anchored to the wrong declaring package).
• New resolved-mode test infrastructure (real analyzer resolution via the workspace package config; Isolate.resolvePackageUri-anchored fixture) covering the validator rejection, alias tracking, and the opt-out.
• Goldens: foreign_signal_value_read (incl. callable/probe/opt-out cases) and foreign_signal_name_collision; integration test asserting rebuild-on-flip through real generated output.
• CHANGELOG scoped (pure-consumer files still pass through verbatim; @SolidQuery doesn't synthesize source: from foreign deps; .untracked scope; Resource.value deprecated → state covered). SPEC §5.1 corrected: SignalBase is declared in package:solidart.

Version: 3.0.0-dev.11.

Verification

dart test packages/solid_generator/ — 380 pass, from both repo root (CI form, -r github --fail-fast) and the package dir. Integration tests pass per-file. dart format clean; dart analyze --fatal-infos only the 2 pre-existing avoid_print infos.