fix(plan): surface context when Seer produces no solution

[MathurAditya724]

When sentry issue plan completes but Seer can't produce a code fix, the output now shows:

• The reason from the API (when available), e.g. "root cause is infrastructure-level"
• The root cause description that was analyzed
• The files Seer examined during analysis

Previously it just said "No solution found. Check the Sentry web UI for details."

Testing

bun test test/types/seer.test.ts — 22 tests pass (10 new for extractNoSolutionReason and extractExaminedFiles).

Closes #951

[github-actions]

PR Preview Action v1.8.1
🚀 View preview at https://cli.sentry.dev/_preview/pr-953/
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[github-actions]

Codecov Results 📊

✅ 6880 passed | Total: 6880 | Pass Rate: 100% | Execution Time: 0ms

📊 Comparison with Base Branch

Metric	Change
Total Tests	📈 +22
Passed Tests	📈 +22
Failed Tests	—
Skipped Tests	—

All tests are passing successfully.

❌ Patch coverage is 55.45%. Project has 14077 uncovered lines.
❌ Project coverage is 76.99%. Comparing base (base) to head (head).

Files with missing lines (2)

File	Patch %	Lines
src/commands/issue/plan.ts	1.30%	⚠️ 76 Missing
src/types/seer.ts	85.12%	⚠️ 18 Missing

Coverage diff

@@            Coverage Diff             @@
##          main       #PR       +/-##
==========================================
- Coverage    77.05%    76.99%    -0.06%
==========================================
  Files          319       319         —
  Lines        60944     61166      +222
  Branches         0         0         —
==========================================
+ Hits         46953     47089      +136
- Misses       13991     14077       +86
- Partials         0         0         —

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Generated by Codecov Action

[MathurAditya724]

fix-ci: attempt 1 — lint failures: cognitive complexity in buildPlanData, return undefined in seer.ts, and formatting in the test file. straightforward fixes.

[MathurAditya724]

All CI checks green, self-review clean — marked ready for review.

Changes: when sentry issue plan finishes but Seer can't produce a code fix, the output now includes the API's reason string, the root cause description analyzed, and which files were examined. The previous bare "No solution found" message is replaced with structured context. --json consumers get the same data in a no_solution_context field (omitted when there's a valid solution).

[MathurAditya724]

Live testing results

Tested against 3 real issues (DOCS-84Y, CLI-A0, SENTRY-5PE8). The no-solution context now shows root cause description + examined files instead of the bare message.

While testing, discovered a pre-existing issue: extractSolution() searches step.artifacts[] but the API returns solution data directly on the step as step.solution[] + step.description. This means the plan command never extracts a successful solution even when one exists. Filed as #958 — separate from this PR's scope (improving the no-solution message).

[MathurAditya724]

fix-ci: attempt 2 — unit test in api-client.seer.test.ts still expects old triggerSolutionPlanning signature and payload shape, updating to match the new 4-arg signature with causeId and the select_root_cause payload