feat: Modular v2 enhancements — 12 gaps + modernization

[intel352]

Summary

Addresses all 12 gaps identified in the Modular framework audit, making it a more complete foundation for the Workflow engine and other consumers. Also modernizes the entire codebase using gopls quickfixes.

Core Lifecycle (Section 1)

• Config-driven dependency hints: WithModuleDependency(from, to) builder option injects edges into the dependency graph before resolution
• Drainable interface: PreStop(ctx) called before Stop() for graceful drain of in-flight work, with configurable WithDrainTimeout(d)
• Application phase tracking: Phase() method returning AppPhase enum (Created → Initializing → Initialized → Starting → Running → Draining → Stopping → Stopped), emits EventTypeAppPhaseChanged CloudEvents
• Parallel init: WithParallelInit() initializes modules at the same topological depth concurrently via errgroup

Services & Plugins (Section 2)

• Type-safe service helpers: RegisterTypedService[T] / GetTypedService[T] generic functions with compile-time type safety
• Service readiness events: OnServiceReady(name, callback) fires immediately if registered or defers until registration
• Plugin interface: Plugin / PluginWithHooks / PluginWithServices interfaces with WithPlugins(...) builder option

Configuration & Reload (Section 3)

• ReloadOrchestrator integration: WithDynamicReload() wires the orchestrator into the app lifecycle
• Config file watcher: modules/configwatcher package using fsnotify with debounced change detection
• Secret resolution hooks: SecretResolver interface + ExpandSecrets() for ${prefix:path} patterns (handles maps, nested maps, and slices)

Observability (Section 4)

• Slog adapter: SlogAdapter wrapping *slog.Logger with With() / WithGroup() chaining
• Module metrics hooks: MetricsProvider interface + CollectAllMetrics(ctx) for vendor-neutral metric collection

Code Quality

• Thread-safe EnhancedServiceRegistry with sync.RWMutex (safe for parallel init)
• ErrDynamicReloadNotEnabled sentinel error
• ConfigWatcher implements Module interface
• gopls modernization across 63 files: interface{} → any, reflect.TypeOf → reflect.TypeFor[T], reflect.Ptr → reflect.Pointer, manual loops → slices.Contains/maps.Copy, C-style for → range N

Design

See: docs/plans/2026-03-09-modular-v2-enhancements-design.md

Implementation Plan

See: docs/plans/2026-03-09-modular-v2-enhancements.md

Test plan

• All 12 features have dedicated test files with edge cases
• go test -count=1 -race ./... passes (root + configwatcher packages)
• go build ./... compiles clean
• Pre-existing feeders/yaml.go vet errors are unrelated to this PR

🤖 Generated with Claude Code

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