feat(chat): preserve single newlines for ZCode replies

[Ni7e]

Problem: ZCode replies render differently in the Ghostex chat view than in the ZCode terminal. The TUI paints every soft-break newline as its own row (glyph status lines, emoji lists, em-space indentation), but the chat view collapsed the same message into one flowing paragraph, scattering the indentation mid-sentence.

Root cause: sessionChatPreservesAgentLineBreaks is an opt-in allowlist per agent family. The feature landed in 6cf849b (2026-09-14) listing Pi, Hermes, and Antigravity; ZCode became a chat agent family one day later (94f62db) and was never added. remarkSessionChatHardBreaks therefore never fires for ZCode transcripts.

Fix: add zcode to the family check, and refresh the CDXC:SessionChat WHY/DECISION comments. The 2026-09-14 decision to leave Claude, Codex, Grok Build, and Cursor unchanged is untouched — ZCode simply was not covered by it.

Verification: root tsc --noEmit passes (the only errors are pre-existing @/apps/web/... resolutions from an uninitialized submodule in my worktree, reproducible without this change). Rendering behavior for ZCode now matches the existing Pi/Hermes/Antigravity treatment: one rendered row per source line, paragraph breaks on blank lines.

Note

Preserve single newlines for ZCode replies in sessionChatPreservesAgentLineBreaks

Extends the agent-family predicate in session-chat-presentation-provider.tsx to return true when the transcript family is zcode, so ZCode assistant replies keep single newlines. Updates the SessionChatAgentLineBreaksContext comment to document ZCode's one-row-per-line TUI behavior.

^{Macroscope summarized d3f8bdb.}

Summary by CodeRabbit

• Bug Fixes
  • ZCode assistant responses now preserve single line breaks instead of collapsing them into a single paragraph.
  • Existing terminal formatting behavior remains unchanged.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: e339c67c-20da-4afd-b161-4ea1fa1ddcaf

📥 Commits

Reviewing files that changed from the base of the PR and between 9e308c3 and d3f8bdb.

📒 Files selected for processing (1)

• packages/core-ui/chat/session-chat-presentation-provider.tsx

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📝 Walkthrough

Walkthrough

The chat presentation provider now preserves single newlines in ZCode assistant replies. The related documentation identifies ZCode as a preserving agent family and records unchanged OMP terminal behavior.

Changes

ZCode line-break handling

Layer / File(s)	Summary
Preserve ZCode line breaks packages/core-ui/chat/session-chat-presentation-provider.tsx	sessionChatPreservesAgentLineBreaks now returns true for the zcode agent family. The documentation comment lists ZCode with the existing preserving terminals and notes unchanged behavior for other terminals.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~5 minutes

Change: Bug fix

Suggested reviewers: maddada

Merge Risk: ⚪ Minimal · up to d3f8b

No actionable correctness or availability risk is established for this focused rendering change.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 1 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: preserving single newlines in ZCode chat replies.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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