refactor: reduce complexity of execute_impl in upload_build_attachment.rs

[github-actions]

What was complex

UploadBuildAttachmentResult::execute_impl() in src/safe_outputs/upload_build_attachment.rs was flagged by Clippy's too_many_lines lint at 267/100 lines. It combined build-ID reconciliation, artifact-name-prefix/validation, allow-list checks, extension checks, attachment-type resolution, staged-file path/integrity validation, SHA-256 verification, ADO API coordinate resolution, and the HTTP PUT + response handling all inline in one function.

What changed

Split the function into 9 focused, independently-testable helpers (following the existing Result<T, ExecutionResult> early-return pattern already used elsewhere in this module, e.g. update_github_issue.rs):

• resolve_effective_build_id — reconciles agent-supplied build_id with the current run
• resolve_final_artifact_name — applies name-prefix, re-validates charset, checks the artifact-name allow-list
• validate_file_extension — checks the file extension against allowed-extensions
• resolve_attachment_type — resolves and validates the {type} URL segment
• resolve_staged_file — canonicalizes/validates the staged file path, size integrity, and size limit
• read_and_verify_staged_bytes — reads file bytes and verifies the SHA-256 hash
• resolve_timeline_coords (+ new TimelineAttachmentCoords struct) — resolves ADO org/project/token/plan/timeline/record IDs
• upload_timeline_attachment — builds the URL, performs the PUT, and translates the HTTP response

execute_impl() is now a short orchestration function (~50 lines) that delegates to these helpers.

Verification

• No public API signatures changed; no observable behaviour changed.
• All existing comments preserved.
• cargo test — full suite: 3322 passed, 0 failed (including all 39 tests in upload_build_attachment::tests).
• cargo clippy --all-targets --all-features — clean.
• cargo clippy -- -W clippy::too_many_lines — no longer flags this file (previously 267/100).

Before/after complexity

	Before	After
execute_impl line count (Clippy too_many_lines)	267/100	below threshold

Warning

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Generated by Cyclomatic Complexity Reducer · auto · 102.8 AIC · ⌖ 13.2 AIC · ⊞ 11.4K · ◷

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