test: cover the Linear GraphQL layer end to end

[seraph-pixelperfect]

Closes #29
Depends on #49

What this does

A coverage audit + gap-fill for issue #29 ("src/linear.ts — every GraphQL operation — has zero coverage"). The issue's premise was partially stale: thirteen stacked PRs (#37–#49) already added fetch-stubbed, command-level coverage asserting most GraphQL document shapes transitively (225 tests / 19 files at the base of this branch). This PR audits every export in src/linear.ts, cites where each operation's document is already asserted, and adds two new transport-level test files (functions in src/linear.ts called directly against a stubbed fetch) only for the real gaps:

• test/graphql-layer.test.ts (24 tests) — operations
• test/graphql-layer-errors.test.ts (16 tests) — mapLinearError end to end through linearRequest

Net: 225 → 265 tests (21 files), +40 tests, zero source changes.

Gaps filled (all had zero coverage before)

1. fetchViewer — exact document query { viewer { id name email } } (only a loose transitive toContain('viewer') existed via --assignee me).
2. fetchTeams — the query Teams { teams { nodes { id key name } } } document had no assertion anywhere (the teams command has no test file).
3. deleteIssue — mutation DeleteIssue and its success:false branch had no assertion anywhere.
4. resolveStateIdByName (via updateIssue stateName) — query TeamStates, case-insensitive matching, the Available states: ... not-found listing, and the Could not resolve team for issue branch were all untested.
5. createIssue omit-null builder — the minimal document (teamId+title only, asserting literal omission of description/labelIds/projectId/cycleId/parentId), the labelNames → resolveLabelIds → labelIds branch (case-insensitive, unknown names skipped, server order), and the team-not-found VALIDATION_ERROR.
6. updateIssue omit-null builder — minimal ($id+$title only, everything else literally omitted) and maximal ($title+$stateId+$assigneeId+$labelIds declared in builder order, unset priority/description/projectId/cycleId omitted).
7. All six mutations' success:false payload branches — every existing suite stubbed success: true only (grep 'success: false' test/ was empty).
8. fetchIssues anti-spin pagination guards — hasNextPage:true with a null endCursor, a non-advancing (repeated) cursor, and an empty page that still claims hasNextPage. (Cursor batching in 50s + remaining-slot first was already covered directly in issues-pagination.test.ts; the empty-page guard for fetchLabels in labels.test.ts.)
9. mapLinearError e2e through linearRequest — the remaining matrix: HTTP 400 (incl. the non-JSON-body json()-catch fallback), 403 both sub-branches (message-less → FORBIDDEN; forbidden-message → AUTH_REQUIRED override), 404 plain → NOT_FOUND, 502 → NETWORK_ERROR; GraphQL 200 errors[]: not-found → NOT_FOUND, unauthorized → AUTH_REQUIRED, validation → VALIDATION_ERROR, message text with (at path) + [extensions.code], the extensions: {...} hint for unclassified errors, no-hint UNKNOWN; a non-array errors value ignored; and the LINEAR_AXI_DEBUG=1 stderr dump. Plus the POST request-shape contract (URL, headers, {query, variables} body, default variables: {}). (401/429/500/generic-GQL/network-throw were already covered in rate-limit-retry.test.ts; the direct unit in errors.test.ts stands.)

Coverage audit — every src/linear.ts operation → where its document shape is asserted

Operation	Document asserted in
linearRequest (transport, 429 retry, 401/429/500, network throw, generic GraphQL error)	rate-limit-retry.test.ts; + NEW graphql-layer-errors.test.ts (request contract + full status/GraphQL matrix + DEBUG dump)
fetchViewer	transitive: issues-search.test.ts (--assignee me); + NEW direct, exact document
fetchTeams	NEW graphql-layer.test.ts (zero before)
fetchProjects (+ pagination)	projects.test.ts (direct: doc, fields, cursor batching, hasMore)
fetchCycles (root + per-team docs, team resolution, not-found, pagination)	cycles.test.ts (direct)
fetchIssues (filters, searchIssues, pagination batching)	issues-search.test.ts, issues-pagination.test.ts (direct batching), projects.test.ts (project filter); + NEW anti-spin guards
fetchIssue (detail, --fields extras, --full children, null→undefined)	fields-wiring.test.ts (extras), sub-issues.test.ts (children + null→undefined), comment-list/comment-update-delete/description-file/project-cycle-assignment (ref pre-fetch); + NEW direct minimal/maximal selection
fetchComments (+ pagination)	comment-list.test.ts (direct: doc + pagination), comment-update-delete.test.ts
fetchComment	comment-update-delete.test.ts
fetchLabels (+ pagination, empty-page guard, hasMore)	labels.test.ts (direct)
createIssue (omit-null: description / projectId / cycleId / parentId)	description-file.test.ts, project-cycle-assignment.test.ts, sub-issues.test.ts; + NEW minimal doc, labelNames branch, team-not-found, success:false
updateIssue (omit-null: assigneeId / labelIds / [] / projectId / cycleId / description)	issue-update-assignee-labels.test.ts, project-cycle-assignment.test.ts, description-file.test.ts; + NEW title-only, full combo, success:false
deleteIssue	NEW graphql-layer.test.ts (zero before)
createComment	comment-list.test.ts, comment-update-delete.test.ts; + NEW success:false
updateComment	comment-update-delete.test.ts; + NEW success:false
deleteComment	comment-update-delete.test.ts; + NEW success:false
resolveTeamId (query TeamByKey)	cycles.test.ts (incl. filter doc), description-file/labels/project-cycle-assignment/sub-issues.test.ts
resolveProjectId (query ProjectByName)	project-cycle-assignment.test.ts
requireProjectId (loud not-found)	project-cycle-assignment.test.ts
fetchActiveCycles (both docs)	project-cycle-assignment.test.ts
resolveCycleIdByNumber (+ not-found)	project-cycle-assignment.test.ts
resolveLabelIds	transitive via update --label in issue-update-assignee-labels.test.ts; + NEW e2e through createIssue
resolveUserId (no-match, multi-match)	issue-update-assignee-labels.test.ts
resolveStateIdByName (query TeamStates)	NEW graphql-layer.test.ts (zero before)
withExtraFields + field fragments	fields-wiring.test.ts (documents with --fields)
mapLinearError	unit: errors.test.ts; e2e: rate-limit-retry.test.ts; + NEW full matrix in graphql-layer-errors.test.ts

Local gates (all run at HEAD of this branch)

$ pnpm build      → tsc, clean
$ pnpm lint       → eslint ., clean
$ pnpm run build:skill -- --check
                  → skills/linear-axi/SKILL.md is up to date.
$ pnpm test
 Test Files  21 passed (21)
      Tests   265 passed (265)      ← baseline 225 in 19 files, +40
$ pnpm run format:check
                  → 18 pre-existing warnings (same file set as main; CI does not run this gate)
$ pnpm exec prettier --check test/graphql-layer.test.ts test/graphql-layer-errors.test.ts
                  → All matched files use Prettier code style!

Latent issues found during the audit (documented, NOT fixed — no source changes in this PR)

• linearRequest 200-with-non-JSON success path resolves undefined: if the server answers HTTP 200 with a non-JSON body, body becomes null (the json() catch) and (body as { data: T }).data is undefined, so callers fail later with a raw TypeError (e.g. reading .viewer) instead of a structured AxiError. Only reachable with a misbehaving server/proxy; left as-is since fixing changes behavior and exceeds this PR's no-product-change scope.
• Observation (not a bug): createIssue declares $title: String! while updateIssue declares $title: String — consistent with Linear's create-vs-update input nullability; the new tests pin both.

Stacked-PR note

Stacked on #49 (stack: #37→#38→#39→#40→#41→#42→#43→#44→#45→#46→#47→#48→#49). No CI checks appear here — ci.yml only triggers on PRs targeting main. CI runs when retargeted to main after the stack merges; local gates above are the evidence. Not retargeting.

CI caveat: GitHub Actions billing/spending-limit rejections render like check failures. If a check shows red with no log output, check gh run view <run-id> / the jobs API for a billing annotation or an empty steps list with a ~3-4s duration — that is a quota block, not a test failure; in that case local output above is the evidence and the run should not be retried.

Identity note

Posted by an automated agent dispatch authenticated as seraph-pixelperfect, for human review — not self-approved. Merge is a human decision.

[ghostinprod-pixelperfect]

Superseded by merged rc/0.2 PR #52 (commit ad6b141), which consolidated this write/transport stack with validation and review fixes.