Claude transcript-dir lookup must survive underscore paths and slug misses

Traceability

• Spec ID: 73-claude-transcript-dir-underscore-slug
• Story: QoderAI/better-harness#73
• Status: Implemented

Intent

workspaceToClaudeSlugVariants() folds /, \, ., and drive-letter : into -, but never folds _. Claude Code does fold _ when it names the directory under ~/.claude/projects/, so every workspace whose path contains an underscore resolves to a nonexistent transcript root: the run succeeds and reports 0 sessions, which reads as "no evidence" rather than "wrong lookup". The Story confirms the diagnosis by junctioning the underscore spelling onto the real folder, which turned 0 sessions into 15 of 15 with evidenceModesession-rich.

Slug guessing is the deeper problem: the slug only selects which folder to open, and isWorkspaceMatch() already re-checks the transcript cwd one step later. A slug miss must therefore degrade to reading the recorded cwd, so the next character Claude Code folds does not silently zero out session evidence again.

Acceptance Scenarios

• AC-1: workspaceToClaudeSlugVariants("C:\\work\\my_project") puts c--work-my-project (underscore folded together with . and separators) first, and keeps the unfolded c--work-my_project spelling as a later fallback variant.
• AC-2: A Claude fixture whose transcript lives under an underscore-folded project directory discovers its sessions through sources instead of reporting zero eligible sessions.
• AC-3: When no slug variant directory exists, sources scans <home>/projects/*, keeps the directories whose transcripts record a cwd inside the selected workspace, reports the claude-project-jsonl root as exists: true, and analyzes those sessions. Unrelated project directories in the same root are not adopted.
• AC-4: Existing behavior is unchanged: dotted workspaces keep their dot-substituted primary slug, dotless Unix workspaces and Windows drive paths keep their previous variants, and a workspace with no transcripts anywhere still reports 0 sessions with the missing-required-root warning.

Non-goals

• No change to other platform slug functions (Cursor, Qoder, Qwen, Pi, Workbuddy); the Story evidence is Claude-specific.
• No blanket [^a-zA-Z0-9] fold. The Story evidences _; the cwd fallback covers any further character class without guessing Claude Code's alphabet.
• No change to the missing-required-root warning shape or to verdict/exit-code semantics. The cwd fallback removes the false-negative case instead of turning it into a failure.

Plan and Tasks

• scripts/session-analysis/platforms/claude.mjs:
  • Fold _ alongside . in the primary slug variants, keeping the narrower .-only and separator-only classes as ordered fallbacks. Adding variants is additive because discovery probes every entry in root.paths.
  • Add a bounded cwd-based recovery in discoverSourceRoots(): when none of the slug paths exist, list <home>/projects and keep the directories whose .jsonl transcripts record a cwd that matches the workspace match scope. The recovered paths are appended to root.paths, so exists and discoverSessions() pick them up with no further changes.
• test/session-analysis-providers.test.mjs: add underscore slug assertions, an underscore-directory provider fixture, and a fallback fixture whose project directory name matches no slug variant while a sibling unrelated project must stay excluded.

Test and Review Evidence

• AC-1/AC-4: node --test test/session-analysis-providers.test.mjs (underscore, dotted, Unix, and Windows slug assertions).
• AC-2/AC-3: same file, fixtures "Claude provider discovers transcripts for underscore workspace paths" and "Claude provider recovers transcripts from the recorded cwd when no slug variant matches".
• Regression safety: node --test test/session-workspace-provider.test.mjs test/session-analysis-claude-facets.test.mjs test/session-analysis.test.mjs.
• Risk: low. The slug change only reorders/extends variants for paths containing _, which previously resolved to nonexistent roots. The cwd scan runs only when every slug variant is missing — today's zero-session path — and is bounded by directory, file, and line caps.