Enrich fork-point and branch nav labels with message summaries

[cboos]

Problem

Fork points and branches whose anchor message isn't user/assistant text
rendered with an empty preview — Fork point (2 branches) and Branch • <uuid8>
— which makes a session's fork structure hard to follow (especially the
tool-flow forks that dominate long, tool-heavy sessions).

What this does

Give fork points and branches a type-aware label:

• Fork point on a tool_use / thinking message →
  Fork point • Bash — <description> / … • Thinking.
  (_fork_point_preview previously returned "" for any non-text content.)
• Branch whose first message has no user text → fall back to a type-aware
  summary of its first meaningful message (Bash — <description> / Thinking),
  while still preferring the branch-local user text when present — preserving
  the /exit ("No response requested.") case and the spawned-agent inner-prompt
  exclusion (the existing test_branch_label_source invariants stay green).

Adds two small helpers (_tool_summary_label, _entry_nav_summary). This is
pure labeling — no change to fork detection.

Tests

test/test_fork_branch_labels.py covers the helpers plus the tool_use/thinking
fork-point and branch cases.

Context

Split out of the investigation into a DAG "branch-happy" staircasing issue
(spurious forks from max_tokens assistant continuations). The fork-detection
fix is a separate follow-up; this legibility improvement stands on its own.

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features

  • Improved navigation previews for branches and fork points with type-aware labels that better handle tool usage, thinking content, and descriptions.
  • Enhanced branch preview computation with intelligent fallback to display meaningful summaries for all content types.

• Tests

  • Added comprehensive test coverage for navigation label generation and type-aware fork point preview functionality.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: fdc4dec7-8de9-4ac6-acb0-756d1220dc05

📥 Commits

Reviewing files that changed from the base of the PR and between 0e478be and c3a1b34.

📒 Files selected for processing (2)

• claude_code_log/renderer.py
• test/test_fork_branch_labels.py

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📝 Walkthrough

Walkthrough

This PR enhances transcript navigation labels in the renderer by introducing type-aware summary generation. New helper functions _tool_summary_label() and _entry_nav_summary() format tool-based and thinking-based labels. These are integrated into _fork_point_preview() and _build_branch_header() to improve preview text for branches and fork points that originate from tool calls or thinking content rather than user text.

Changes

Type-aware transcript navigation labels

Layer / File(s)	Summary
Summary label helper functions claude_code_log/renderer.py	Two new helpers generate type-aware preview labels: _tool_summary_label() formats tool-based labels as Tool — description with truncation; _entry_nav_summary() selects summaries from transcript entries based on content type (tool use, thinking, or text).
Tests for summary label helpers test/test_fork_branch_labels.py	Comprehensive unit tests validate helper functions, including test utilities _meta() and _entry(). Tests cover tool-label formatting, description omission rules, truncation behavior, and entry-type-specific summary output for tool, thinking, and text entries.
Fork-point preview type-aware refactor claude_code_log/renderer.py, test/test_fork_branch_labels.py	_fork_point_preview() is refactored to apply the new helpers: tool-based fork points now produce Tool — description labels; thinking fork points show a fixed "Thinking" label; tool-result fork points show tool-name-based result text. Tests verify formatted labels for tool-use fork points and unchanged output for text/thinking fork points.
Branch header fallback and documentation claude_code_log/renderer.py	Inline documentation clarifies preferred scanning behavior in _build_branch_header(). A fallback path is added: when no user-text preview is found, _entry_nav_summary() derives the branch preview from the first branch DAG-line entry that yields a summary, enabling informative labels for branches starting with tool or thinking content.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• daaain/claude-code-log#184: Both PRs modify the branch-header preview logic in _build_branch_header(), with this PR adding type-aware fallback via _entry_nav_summary() after the DAG-based scan from #184.
• daaain/claude-code-log#131: Both PRs update renderer-level fork-point and branch preview label generation in _fork_point_preview() and _build_branch_header() for within-session navigation, extending prior fork rendering changes.

Poem

🐰 Types of summaries, neat and clear,
Tools and thoughts now appear!
Preview labels, branching true,
One-line wisdom for the review.
Fork points navigate the way,
Through the transcript, come what may! 🌿

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 27.78% which is insufficient. The required threshold is 80.00%.	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 'Enrich fork-point and branch nav labels with message summaries' directly and clearly reflects the main change: improving navigation labels with type-aware message summaries for fork points and branches.
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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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch dev/label-fork-points-and-branches

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