fix: stabilize agent streaming and conversation UX

[liyangbing]

Summary

• stream Claude Code partial text and thinking frames without duplicating completed assistant blocks
• make conversation SSE rendering resilient to buffered deltas, trailing done frames, refresh recovery, provider rejection, and dispatch cancellation
• fix capability credential selection, dialog viewport behavior, daemon command copying, and login failure handling
• preserve implicit primary-agent routing for SSH URLs and email addresses without rerouting invalid explicit mentions
• ensure run terminal states persist with an independent bounded context

Architecture boundaries

• Claude-specific stream translation remains owned by the daemon adapter
• durable run state and conversation routing remain owned by the server/store
• SSE buffering, recovery, and presentation remain owned by the web client
• the terminal-state persistence invariant is documented in CONTRIBUTING.md

No API schema, database schema, migration, or sqlc query contract changes are included.

Verification

• make check-go
• make check-store with an isolated parsar-pr-check Compose project
• make check-web
• make check-cli
• make check-hygiene
• npm production build for @parsar/web
• manual browser verification against the restarted web/server/daemon stack

The isolated migration-test container and volume were removed after verification.