[Creed1759]

…and correlation id boundary specs

Closes #1203, Closes #1200, Closes #1202, Closes #1201

#1203 — apps/api: AppService.getHealth degraded branch returns 503 and is asserted in controller tests

• Updated AppController.health to return HTTP 503 (SERVICE_UNAVAILABLE) when AppService.getHealth reports a degraded status and HTTP 200 (OK) when healthy, enabling load balancers and uptime monitors to accurately detect dependency degradation.
• Added explicit unit tests in apps/api/src/app.controller.spec.ts asserting both HTTP 200 on healthy checks and HTTP 503 on degraded checks.

#1200 — scripts/validate-contracts.js: distinguish missing contract directory from compilation failures

• Track missing contract directories in a separate missing array distinct from cargo compilation failures (failed).
• Log explicit failure details with expected directory paths when a contract directory is absent.
• Report Passed, Missing, and Failed counts separately in the final summary.
• Guard the --check-drift gate by failing immediately and skipping drift detection when any contract was missing or failed to compile.

#1202 — scripts/validate-contracts.js: dynamically derive contract list from filesystem

• Replaced the hardcoded contract array with dynamic directory discovery under packages/contract/contracts filtering for valid directories containing Cargo.toml.
• Merged discovered contracts with expected contracts declared in manifestKeysByContract sorted deterministically.
• Added a validation check under --check-drift that fails loudly if any discovered contract lacks a mapping in manifestKeysByContract.

#1201 — packages/config: test 64-char boundary and fallback for sanitizeCorrelationId

• Added comprehensive unit tests in packages/config/scripts/tests/check-shared-config.test.mjs verifying:
  • Valid 64-character correlation ID strings pass through unchanged.
  • Valid 65-character strings are truncated to exactly 64 characters.
  • Empty strings and strings consisting purely of invalid characters return null.
  • resolveCorrelationId({}) defaults to the expected local PID fallback (/^local-\d+$/).

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