Add VSC v2.8.1 release notes

Author: DigiEmu

docs/releases/v2.8.1-comparison-runner-script.md

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+# VSC v2.8.1 — Comparison Runner Script
+
+Release: v2.8.1  
+Status: released  
+Project: DigiEmu VSC / VSC Core
+
+## Summary
+
+VSC v2.8.1 adds the first executable comparison runner for the Node/Go conformance comparison profile introduced in v2.8.
+
+The runner reads the v2.7 conformance fixture index, executes the Go verifier against each fixture, parses the machine-readable JSON result, and compares the actual verification class against the expected fixture result.
+
+Core principle:
+
+```text
+same fixture input → same verification result class
+```
+
+## Added
+
+- New comparison runner script:
+
+```text
+scripts/compareConformanceResults.js
+```
+
+- New CLI command:
+
+```powershell
+npm run vsc -- compare:fixtures
+```
+
+## Updated
+
+- README documentation
+- v2.8 conformance documentation
+- VSC CLI command routing
+
+## Comparison behavior
+
+For each fixture, the runner:
+
+1. Reads `conformance/v2.7/fixture-index.json` 
+2. Runs:
+
+```powershell
+go run ./cmd/vsc-go verify-bundle --json <fixture>
+```
+
+3. Parses the JSON verification result
+4. Compares `actual result` against `expected_result` 
+5. Derives the semantic exit-code class from the JSON `result` 
+6. Prints a comparison table
+7. Returns final comparison status
+
+## Important Windows note
+
+On Windows, `go run` may flatten or obscure non-zero exit codes in some execution contexts.
+
+For this reason, the comparison runner treats the JSON field:
+
+```json
+"result": "PASS" | "FAIL" | "ERROR"
+```
+
+as the primary semantic truth and derives the expected exit-code class from it.
+
+## Validated fixtures
+
+```text
+pass-basic                → COMPARE_PASS
+fail-checksum-mismatch    → COMPARE_PASS
+error-malformed-manifest  → COMPARE_PASS
+```
+
+Expected final output:
+
+```text
+Final result: COMPARE_PASS
+```
+
+## Validation commands
+
+```powershell
+npm run vsc -- compare:fixtures
+npm run vsc -- verify-all
+```
+
+Expected:
+
+```text
+compare:fixtures → Final result: COMPARE_PASS
+verify-all       → FAIL: 0
+```
+
+## Scope
+
+v2.8.1 does not change the verification semantics of VSC.
+
+It adds an executable comparison layer for checking that fixture-level conformance results remain aligned with the declared comparison profile.
+
+## Known cosmetic issue
+
+The comparison table header is currently functional but visually tight:
+
+```text
+fixture_id        expectedactual  exp_exitact_exitcomparison
+```
+
+This can be improved in a follow-up patch, for example:
+
+```text
+v2.8.2 — Runner table formatting + optional --json output
+```
+
+## Release meaning
+
+v2.8.1 turns the v2.8 Node/Go comparison draft from documentation into an executable conformance check.
+
+This strengthens VSC as a portable evidence verification layer by making verifier behavior more reproducible, comparable, and testable across implementations.