Add neutral FeatureFramework lifecycle observation SPI

[remdui]

Summary

Implements the FeatureFramework 1.7.0 neutral lifecycle observation foundation without coupling FeatureFramework to OpenTelemetry or HauntedObservability.

What changed

• added the dependency-free FeatureFrameworkObserver / observation / scope API
• added a bounded operation context containing only operation kind and optional framework-owned FeatureId
• observes public host lifecycle operations at the serialized host boundary
• observes FEATURE_LOAD at the actual shared startup path, including startup/reload/reset-driven loads
• preserves parent/child observation scope nesting without inventing duplicate high-level operations during internal graph reconciliation
• added construction-time observer injection to Paper and Velocity hosts with a reusable no-op default
• preserves the existing FeatureHostComposition constructor for source/binary compatibility
• keeps observer callback failures fail-open for RuntimeException; Java Errors remain fatal and are not swallowed
• provides a true default no-op fast path and skips terminal classification when a custom observer filters an operation by returning noop()
• enforces the privacy/cardinality boundary and bans OpenTelemetry/HauntedObservability implementation coupling from API/core sources
• aligns the build with HauntedPlatform 1.3.0, DataProvider 3.3.0, and DataRegistry 1.15.0
• documents the FeatureFramework -> DataRegistry -> DataProvider observation layering and the 1.7 observability release order

Operation vocabulary

HOST_START, HOST_STOP, FEATURE_LOAD, FEATURE_ENABLE, FEATURE_DISABLE, FEATURE_RECREATE, FEATURE_SOFT_RELOAD, GRAPH_RELOAD, FILE_RESET.

previewFileReset(...) intentionally remains unobserved.

Validation

Exact reviewed head: df4ed64b8b89d427f2b24a38643490fbcd017f20

• CI Lint #130: passed
  • ShellCheck: passed
  • shared HauntedPlatform Maven policy / verify: passed
• CI Tests and Coverage #131: passed
  • full Maven verify: passed
  • external BOM consumption: passed
  • Paper and Velocity platform acceptance: passed
• DataProvider v3.3.0 and DataRegistry v1.15.0 release tags were verified and the reactor resolves against their published artifacts
• current ServerFeatures and ProxyFeatures host-builder call sites remain source-compatible; application observer wiring is intentionally deferred until HauntedObservability exists
• no open review threads or submitted reviews remain

Release boundary

The reactor intentionally remains at 1.6.0 in this implementation PR. After this PR is reviewed and merged, create the guarded 1.7 release from clean main with:

./update_version.sh minor

That script updates the reactor to 1.7.0, runs the full platform-acceptance gate, creates the local release commit, and creates annotated tag v1.7.0. Push the release commit and tag only after that gate succeeds. FeatureFramework 1.7.0 must be published before HauntedObservability 1.0.0.