Resolve #1615: Add Terminus regression coverage

[ayden94]

Summary

Closes #1615.

Adds regression coverage for the existing @fluojs/terminus custom path and HTTP timeout contracts without changing runtime behavior.

Changes

• Added TerminusModule.forRoot({ path }) coverage proving /health and /ready mount beneath the configured prefix and the unprefixed routes are not registered.
• Added HttpHealthIndicator coverage proving timed-out probes abort the underlying fetch signal and surface a deterministic down result.
• Changeset decision: no changeset because this is tests-only coverage for existing documented behavior, with no public API or runtime behavior change.
• Docs decision: no README changes because the existing README/README.ko contract already documents path and timeout semantics; this PR pins them with regression tests.

Testing

• pnpm --filter @fluojs/terminus... build
• pnpm exec biome check "packages/terminus/src/module.test.ts" "packages/terminus/src/indicators/http.test.ts"
• pnpm --filter @fluojs/terminus typecheck
• pnpm --filter @fluojs/terminus test
• LSP diagnostics: clean for changed files

Public export documentation

• Changed public exports include a source-level summary.
• Changed exported functions document matching @param / @returns tags where applicable.
• Source @example blocks and README scenario examples still play complementary roles.

No public exports changed.

Behavioral contract

• No documented behavioral contracts were removed without migration notes.
• New behavioral contracts are documented in the affected package README.
• Intentional limitations are explicitly stated (not silently removed).
• Runtime invariants are covered by regression tests.

No new behavior was introduced; this PR adds regression tests for existing path and HTTP timeout/abort behavior.

Platform consistency governance (SSOT)

• SSOT English/Korean mirror structure remains synchronized for changed governance docs.
• If platform contract docs changed, companion updates include discoverability/docs index, tooling or CI enforcement, and regression-test evidence.
• Any package README alignment/conformance claims are backed by createPlatformConformanceHarness(...) tests.

No governance docs or package README files changed.