[AUTOMATION] feat: clean up managed ledger streaming

[michiosw]

Summary
This cleans up managed ledger streaming by consolidating the authorization-ledger payload contract and tightening stream state typing.

Before this, the payload schema constants/types lived in internal/managedstream/stream.go and tests redefined partial request structs. The stream cursor updated_after was a string, which pushed timestamp parsing/validation into call sites.

Now internal/ledger is the canonical home for the payload contract, and managed stream state uses a typed *time.Time cursor while keeping the on-disk JSON field stable.

Why
This gives kontext-cli a single maintenance path for exporting the hosted authorization ledger:

sqlite.Store.LedgerBatch
-> internal/managedstream.Flush
-> internal/ledger.Payload
-> POST /api/v1/authorization-ledger/batches

This PR does not broaden behavior beyond the cleanup scope.

What changed
Added internal/ledger with canonical payload types/constants
Removed duplicated payload schema/types from internal/managedstream
Strengthened stream state cursor typing (UpdatedAfter *time.Time) with characterization tests
Updated managed observe daemon test to decode the canonical payload
Stopped ignoring probe conn.Close() errors (diagnostic log)

Verification
go test ./internal/managedstream ./internal/managedobserve ./internal/ledger -count=1
go test ./... -count=1
go vet ./...

[michiosw]

• [AUTOMATION] feat: clean up managed ledger streaming #239 👈 (View in Graphite)
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[greptile-apps]

Greptile Summary

This PR centralizes the managed ledger payload contract and tightens stream cursor state handling. The main changes are:

• Adds internal/ledger for authorization-ledger payload types and constants.
• Updates managed stream posting to use the canonical ledger payload.
• Changes managed stream state to keep updated_after as a typed timestamp in memory.
• Preserves the on-disk stream state JSON shape through explicit load and save conversion.
• Logs managed observe probe close errors for diagnostics.

Confidence Score: 5/5

This looks safe to merge.

• No blocking issues found in the changed code.

_{Reviews (1): Last reviewed commit: "feat(managed): consolidate ledger payloa..." | Re-trigger Greptile}