[chore] architecture refactor

[ldmonster]

Overview

Followed: #862

Implements architecture refactoring roadmap (review.md): seven focused, medium-risk improvements covering a data race, a deferred context, two OCP violations, three interface splits, and two structural decompositions. Build is clean; all 26 test packages pass; 5 new test files added (709 insertions, 218 deletions across 16 files).

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What this PR does / why we need it

2.1 — Extract HookTaskFactory (operator.go, new hook_task_factory.go)
initHookManager, initValidatingWebhookManager, and conversionEventHandler each contained an identical anonymous callback building a task.NewTask(HookRun).WithMetadata(HookMetadata{...}).WithLogLabels(...).WithQueueName(...).WithCompactionID(...) chain (~15 duplicated lines, three times). Extracted to HookTaskFactory.NewHookTask(hook, bindingType, info, logLabels). The factory is a zero-value struct field on ShellOperator; no constructor wiring required.

2.2 — Decompose loadHook() into three discrete methods (hook_manager.go)
loadHook() was ~80 lines performing path resolution, --config execution, config parsing, metadata label injection for four binding types, controller wiring, and validation. Refactored into:

Method	Responsibility
fetchHookConfig(hook)	Execute hook --config, parse output, populate hook.Config
enrichHookMetadata(hook)	Inject hook.Name log/metric labels into all four binding type configs
wireHookController(hook)	Construct HookController, init all binding subsystems, set TmpDir

loadHook() now orchestrates only: construct hook → fetchHookConfig → enrichHookMetadata → wireHookController → validate → log.

2.3 — IOProvider interface abstracts temp-file I/O from Hook.Run() (hook.go, new io_provider.go)
Hook.Run() previously called five private prepare*File() helpers that created real OS temp files, making the method impossible to unit-test without a filesystem and manual cleanup. Introduced:

type IOProvider interface {
    PrepareFiles(context BindingContextList, safeName, tmpDir string) (HookRunFiles, func(), error)
}

FileIOProvider{} is the production implementation (writes to tmpDir). Tests can supply any alternative implementation. NewHook injects FileIOProvider{} by default; the field is exported so test code can substitute it. The five prepare* methods are removed; Run() calls h.IOProvider.PrepareFiles(...) and uses the returned HookRunFiles struct for all path references.

2.4 — VersionedConverter registry; remove version switch (config.go)
HookConfig.ConvertAndCheck contained a switch c.Version { case "v0": ... case "v1": ... } — a textbook OCP violation. Introduced the VersionedConverter interface (one method: ConvertAndCheck(data []byte, c *HookConfig) error) and a var versionedConverters = map[string]VersionedConverter{ "v0": v0Converter{}, "v1": v1Converter{} } registry. The switch is replaced by a single map lookup. New versions are added by registering a new struct — no changes to ConvertAndCheck needed.

2.5 — Split KubeEventsManager and ScheduleManager interfaces
Both interfaces previously mixed lifecycle control, entry/monitor management, and channel emission into a single surface.

• KubeEventsManager → MonitorRegistry (CRUD: AddMonitor, HasMonitor, GetMonitor, StartMonitor, StopMonitor, WithMetricStorage, MetricStorage) + EventEmitter (Ch, Stop, Wait). KubeEventsManager composes both.
• ScheduleManager → ScheduleRegistry (Add, Remove) + ScheduleEmitter (Ch, Start, Stop). ScheduleManager composes both.

Callers that only need event consumption can now depend on EventEmitter/ScheduleEmitter; callers that only register watches depend on MonitorRegistry/ScheduleRegistry. The concrete types satisfy all sub-interfaces (verified by compile-time var _ X = (*impl)(nil) assertions in tests).

2.6 — Propagate context.Context through bootstrap.Init() (bootstrap.go, start.go)
Init() previously accepted no context and called context.TODO() in six places — four logger.Log calls, NewShellOperator, and RunDefaultDebugServer. The function signature is now Init(ctx context.Context, logger *log.Logger) and every internal call uses the provided context. The single call-site in cmd/shell-operator/start.go passes the context.Background() that already existed there.

2.7 — Fix CronEntry.Ids data race (schedule_manager.go)
sm.Entries was map[string]CronEntry (value). Mutating cronEntry.Ids[newEntry.Id] on a copy retrieved from the map silently discarded the write; the stored entry was never updated. Under concurrent access the check-then-modify pair was also racy. Changed to map[string]*CronEntry so all reads and writes operate on the same heap object under the existing mutex.