Converge traversal errors to C5 leaves

[coenttb]

Implements the ruled C5 traversal surface from Task #6 and its page-error taxonomy.

• moves the three page values to resource Page namespaces and adds the ruled non-generic page leaves;
• makes traversal clients non-generic and exposes Either<Async.Lifecycle.Error, Traversal.Error>;
• maps lifecycle failures through the left arm and page/traversal failures through the right arm;
• keeps targets and products unchanged (Decompose into per-resource targets and products (ruled family shape) #7 remains serialized behind this change).

Verification: workspace package test --package-path . --fresh --jobs 4 passed (17 tests); workspace package lint --package-path . completed with 38 existing advisory violations.

[coenttb]

BLOCKING — exact-head review of 6b03867.

Changed-surface blocker: the required swift-format lint job failed in https://github.com/swift-foundations/swift-github/actions/runs/30744866716/job/91488652436. Its diagnostics identify formatting violations in seven files changed by this PR: the three resource Client files, GitHub.Organization.Repositories.Client+all.swift, and the three changed Client test files. The failures are line-length, required line-break, and indentation violations, so this exact head does not satisfy the formatting gate.

Exact fixer: the source owner should apply Swift 6.3.3 swift-format output only to those seven changed files, push the resulting head, and return it for independent exact-head review. No source mutation, full-tier dispatch, merge, Task #6 closure, or #7 release was performed.

[coenttb]

Formatting-only replacement head: 0f49fa7f4a4ca30cde29d81f5c7b7522574cddac

Applied swift-format 6.3.3 mechanically to exactly the seven paths reported by the required PR formatter job:

• Sources/GitHub/GitHub.Organization.Repositories.Client+all.swift
• Sources/GitHub/GitHub.Organization.Repositories.Client.swift
• Sources/GitHub/GitHub.Repository.Stargazers.Client.swift
• Sources/GitHub/GitHub.User.Repositories.Client.swift
• Tests/GitHub Core Tests/GitHub.Organization.Repositories.Client Tests.swift
• Tests/GitHub Core Tests/GitHub.Repository.Stargazers.Client Tests.swift
• Tests/GitHub Core Tests/GitHub.User.Repositories.Client Tests.swift

Verification:

• Exact formatter selector: Swift 6.3.3; swift-format --version reported 6.3.3.
• swift-format lint --strict --ignore-unparsable-files over those seven explicit paths exited 0.
• Commit diff: 7 files, 31 insertions, 18 deletions; the complete diff is whitespace/line-wrapping only, with no semantic/API/test-behavior/manifest/workflow changes.
• A fresh package test was not re-originated because the serialized Workspace lane was busy at the immediate non-blocking check. Preserved task-attributed provenance from the prior implementation head: the fresh capped package test passed 17 tests; package lint exited 0 with 38 pre-existing advisories.

Push receipt: 6b038679108f76d156417c89280e7521ecec9991 → 0f49fa7f4a4ca30cde29d81f5c7b7522574cddac on issue-6-c5 (normal fast-forward; no force push).

[coenttb]

SOURCE-CLEAN — exact-head re-review of 0f49fa7.

Checked evidence: this replacement is the direct child of the previously reviewed 6b03867 (#9 (review)). Its complete delta changes exactly the seven formatter-cited files, with 31 insertions and 18 deletions consisting only of Swift 6.3.3 line wrapping and indentation. I re-read the complete two-commit, 23-file PR diff: the declared primitive dependencies, per-resource Page and Page.Error ownership, typed Either split between lifecycle and traversal failures, and corresponding traversal tests are coherent.

Task-attributed evidence from the replacement owner: Swift 6.3.3 format lint passed on all seven replacement paths; a fresh capped package test passed 17 tests; package lint exited 0 with 38 pre-existing advisories.

No changed-surface or policy blocker remains. A qualifying full-tier workflow_dispatch at this exact head is still required before landing; merge and Task #6 completion remain held until that run succeeds.