fix: reduce UI load during streaming sessions

[hsteude]

Summary

• throttle markdown parse/sanitize work during streaming updates
• avoid rebuilding timeline turns for text-only deltas
• remove duplicate active-project SSE connection by routing event consumers through SyncProvider
• remove per-event SSE hot-path logging

Verification

• bun run build (from app-prefixable)

Closes #445
Closes #446
Closes #447
Closes #448

[Copilot]

Pull request overview

This PR focuses on reducing frontend CPU and overhead during high-volume streaming SSE sessions by consolidating event consumption, throttling expensive markdown work, and avoiding unnecessary recomputation in the chat timeline.

Changes:

• Routes event/status/question consumers through SyncProvider to avoid duplicate active-project SSE connections and removes per-event SSE hot-path logging.
• Adds a subscription mechanism to SyncProvider so other contexts (like EventProvider) can consume the same parsed event stream.
• Introduces throttled markdown parsing/sanitization and attempts to reduce timeline recomputation work during streaming deltas.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
app-prefixable/src/pages/directory-layout.tsx	Reorders providers so EventProvider can consume events via SyncProvider.
app-prefixable/src/context/sync.tsx	Adds subscribe() for shared SSE event consumption and removes per-event logging.
app-prefixable/src/context/events.tsx	Removes its own SSE connection and consumes events through SyncProvider.
app-prefixable/src/components/message-timeline.tsx	Adds a “structure” memo intended to limit turn recomputation during text deltas.
app-prefixable/src/components/markdown.tsx	Throttles markdown parse/sanitize work during streaming updates.

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[Copilot]

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated no new comments.