Register event_blobs (tag 11) in conversation-bundle type registry

[colombod]

Summary

The conversation-bundle.json type registry only declares tags 1–4 (role, content, tool_calls, timestamp). The cxdb.ConversationItem v3 schema used by amplifier-bundle-context-intelligence defines additional fields, including event_blobs at AssistantTurn tag 11 — a map<string, array<bytes>> that links BLAKE3 blob hashes to the turns they belong to.

Because tag 11 is not registered, the server's typed projection (view=typed, the default) silently drops event_blobs from HTTP responses. Clients must pass ?include_unknown=1&bytes_render=hex as a workaround, which surfaces the field in the "unknown" section with numeric string keys (e.g., "11" instead of "event_blobs").

Current Behavior

GET /v1/contexts/{id}/turns
→ response.data contains only tags 1-4 (role, content, tool_calls, timestamp)
→ tag 11 (event_blobs) is silently dropped

With workaround:

GET /v1/contexts/{id}/turns?include_unknown=1&bytes_render=hex
→ response.unknown["11"] contains the event_blobs data with hex-encoded BLAKE3 hashes

Expected Behavior

Tag 11 should appear in the default view=typed response under its named key event_blobs, with BLAKE3 hashes rendered per the bytes_render parameter (default: base64).

Proposed Fix

Update fixtures/registry/conversation-bundle.json to declare tag 11:

{"tag": 11, "name": "event_blobs", "type": "map", "required": false}

Ideally the full ConversationItem v3 schema should be registered (tags 1–13 for the top-level item, plus nested AssistantTurn, ToolCallItem, TurnMetrics, etc.), but registering tag 11 alone would unblock the most critical use case: linking blob-stored raw LLM request/response data back to the turns they belong to.

Context

• Client module: cxdb-session-storage in amplifier-bundle-context-intelligence
• Write path: Blobs are written via PutBlob (binary protocol), BLAKE3 hashes are stored in AssistantTurn.event_blobs (msgpack tag 11) and correctly persisted
• Read path: HTTP get_turns drops the field because the projection system skips unregistered tags
• Current client workaround: include_unknown=1&bytes_render=hex + merge unknown section + dual-key lookup ("event_blobs" / "11")
• Server code: server/src/projection/mod.rs:68-82 — only iterates descriptor.fields, unknown tags require include_unknown flag

Broader Discussion

The current conversation-bundle.json only has 4 fields from what appears to be an older schema version. The actual ConversationItem v3 used by the Amplifier ecosystem has ~30 fields across nested structures (ConversationItem → AssistantTurn → ToolCallItem → TurnMetrics, etc.). It would be worth discussing whether to:

1. Minimal fix: Just add tag 11 for event_blobs
2. Full registration: Register the complete ConversationItem v3 schema with all nested types
3. Client-published registry: Allow clients to publish their own type bundles via PUT /v1/registry/bundles/{id} at connection time (the endpoint already exists)