feat(cli): show per-attempt retry detail in checks get [AI-340]

[miliberlin]

What

Adds checkly checks get <check-id> --result <result-id> --include-attempts, which renders the full retry sequence for a result instead of just the final outcome.

A single check run produces one FINAL result plus one ATTEMPT result for each earlier failed try, all sharing a sequenceId. By default only the FINAL result is shown; this flag surfaces the attempts.

$ checkly checks get a1b2c3d4-0000-4000-8000-000000000001 \
    --result 7f3e9a10-1111-4000-8000-0000000000f0 --include-attempts

Login flow · failing · eu-west-1 · 4.2s
...
ATTEMPTS
  #          Status    Location    Duration  Error                      Result ID
  1          failing   eu-west-1   3.9s      Timeout 30000ms exceeded   7f3e9a10-1111-4000-8000-0000000000a1
  2          failing   eu-west-1   4.0s      Timeout 30000ms exceeded   7f3e9a10-1111-4000-8000-0000000000b2
  3 (final)  passing   eu-west-1   4.2s      —                          7f3e9a10-1111-4000-8000-0000000000f0

  View attempt: checkly checks get a1b2c3d4-0000-4000-8000-000000000001 --result 7f3e9a10-1111-4000-8000-0000000000a1

How

• The list endpoint has no server-side sequenceId filter, so attempts are fetched via resultType=ALL in a bounded time window anchored at the result and grouped client-side by sequenceId (ordered oldest-first, so index = run number).
• The extra call is skipped entirely when the result has no retries (attempts === 0).
• Renders attempt number, status, location, duration, and a best-effort short error summary, with the FINAL row marked (final). Works in detail, md, and json (json emits { result, attempts }).

Backend dependencies (both merged)

• AI-223 — resultType=ALL now returns the full FINAL+ATTEMPT sequence (was returning empty).
• AI-219 — test-session result detail endpoint (related milestone work).

Changes

• rest/check-results.ts — resultType accepts ALL; documented from/to as UNIX seconds; added errorGroupIds.
• formatters/check-result-detail.ts — groupAttemptsBySequence, extractResultErrorSummary, formatAttemptsSection; optional extraSections on formatResultDetailWithNavigation.
• commands/checks/get.ts — --include-attempts flag (dependsOn: result), windowed fetch + grouping, per-attempt nav hints.
• ai-context/references/investigate-checks.md — documents the flag.

Testing

• New unit tests (grouping, error extraction, terminal+md section, empty cases); full result-detail spec passing.
• Verified locally against real check results with ./bin/run checks get <id> --result <rid> --include-attempts.
• tsc --noEmit and eslint clean.

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