fix(init): say why trail init couldn't read past sessions

[rushabhnagda11]

Found while rehearsing the new onboarding (#585) for the 2026-10-19 metrics review.

What

When the past-session read fails, trail init printed:

· couldn't read your past sessions this time; trail init again tries again

In rehearsal the cause was a claude CLI whose OAuth session had expired (claude -p returns is_error: true, "Failed to authenticate: OAuth session expired"). Running trail init again just fails the same way. Now:

· couldn't read your past sessions: Claude Code didn't answer. Check `claude` is signed in, then run trail init again

reason: "no_claude" (no claude on PATH) used to print nothing at all. It now gets its own line.

Safety

• Copy only. finishPastRead, the read mark and the retry behaviour are untouched; both reasons already left the mark unwritten, so "run trail init again" is accurate.
• graft init never runs the past read (it's gated on TRAIL), so graft output is unchanged.

Test

Built the branch and ran trail init in a sandboxed $HOME with four seeded transcripts and a signed-out claude. The new line prints as above.

🤖 Generated with Claude Code

[trailhq-graft]

🌱 graft blast radius

Nothing outside this diff depends on it. 1 area changed; no indexed dependents at depth 2.
Tests: no test reaches CLI Initialization.
Tag: @anirudhkumar-nanonets — CLI Initialization · @shhdwi — CLI Initialization

Who knows this code — 2 people across 1 area

Area	Who knows it
CLI Initialization · changed	@anirudhkumar-nanonets — 53 commits, last today · @shhdwi — 23 commits, last 2mo ago

Ownership is git history over each area's own files, weighted towards recent work (120-day half-life). Merge commits and bots are dropped, and you are dropped from your own PR. A name with no @ has no GitHub handle in its commit email — tag them by hand, or add a .mailmap entry. A suggestion from history, not a CODEOWNERS rule.

Test signal per changed area — 1 ✗

Reached = a node under a test path has a resolved edge into the changed symbol. It undercounts anything called indirectly — through a CLI, a spawned process or a dynamic import — so read a low ratio as “look here”, never as a coverage gate.

• ✗ CLI Initialization — 0 of 1 reached · no test file reaches it
  • not reached: runInitCommand

_{graft blast · origin/main...HEAD · depth 2 · 1 changed file}

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