[TST-E3] test: the emission and ingestion tests that only read the pinned spec share its one binding

[Blind-Striker]

📝 Description

What does this PR do?
It is the third PR of TST-E3's first half. Eight emission and ingestion test classes that only read the pinned spec now take it from the session-shared Support/PinnedBinding fixture that #434 added, instead of ingesting or binding it themselves:

Class	Reads
Generator/Emission/ExperimentalSurfaceEmissionTests	Plan (its diagnostic variant is still a local with copy)
HandWrittenDoorRemarksTests	Document
HandWrittenExperimentalDoorTests	Document, Curation
HandWrittenTransportTableTests	Document (both table rows kept)
OptionalConverterEmitterTests	Plan.Models (its private helper is now synchronous, since nothing is awaited)
SessionScopedEventEmissionTests	Plan
SourceEmitterTests	Plan (the full union and registry comparisons stay full)
Generator/Ingestion/PinnedSpecSmokeTests	Document, for its ordinary landmark tests

The determinism test stays independent. PinnedSpecSmokeTests' determinism test still ingests twice through its own helper, and now carries a comment saying why: comparing a cached result with itself proves nothing.

Pinned ingestions for these classes go from 22 to 3 per session: the shared initialization plus the two deliberate determinism ingestions. All 40 test names, 140 assertions and 4 argument rows are unchanged, and no test mutates the shared objects.

The files GEN-E3 is editing, PinnedBinding, BindingTestHost, BindingScenarioData and SpecScenario are unchanged.

🔄 Type of Change

• 🧪 Test improvements

🎯 Protocol & API Surface

• No change to the public API surface
• Nothing under external/, spec/ or src/ was touched

🧪 Testing

• Ingestion count: measured with temporary instrumentation in the implementer's worktree, then removed: 22 completed ingestions before, 2 plus the fixture's 1 after.
• Harness evidence: the dispatch harness ran the RepositoryGates guards (93/0), verify-clones (0 new) and the whole Tools.Tests project under [(Category!=Packaging)&(Category!=NativeAot)] (1991/0, exit 0) on the committed tree.
• Review: a fresh read-only review found no defects, out-of-scope changes or notes. It traced every adopter. The diagnostic variant uses with, the emission only enumerates Plan.Models, the determinism helper is untouched, and the seven migrated smoke tests inspect ingestion landmarks, not repeated-execution behaviour.
• Rebase: written on [TST-E3] test: the pinned spec is bound once per session for the binding tests that only read it #434's head and rebased onto its merge, with no conflict.

✅ Completion Gate

Local check (quality-gates.md) on head 4630df90, base 321ce2fc. Every step's own exit code was read:

• slopwatch: zero findings
• dotnet build --configuration Release: 0 warnings, 0 errors
• dotnet format whitespace / dotnet format style --severity warn: no changes
• verify-clones: passed, 0 new (tests 5.52%)
• OpenCode.Sdk.Tools.Tests (all but NativeAot): 2004, 0 failed
• OpenCode.Sdk.Tests (all but ServiceElection/NativeAot): 8390, 0 failed

The host runs Bun 1.4.3, a maintainer-named off-pin host (OPENCODE_SDK_TESTS_BUN_MISMATCH=allow); the pin is 1.4.2.

✅ Code Quality Checklist

• No new suppression
• No tests skipped, weakened, or deleted to make the suite pass

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