Preserve untouched document fields in files update

[robzolkos]

Summary

Fixes a data-loss hazard in basecamp files update for documents. When callers updated only --title or only --content, the untouched field could be cleared because document updates are backed by a destructive PUT-style API contract. The CLI now fetches the current document first and preserves the existing title/content before applying the requested change, so partial document updates behave the way users and agents expect.

Ref: https://3.basecamp.com/2914079/buckets/46292715/card_tables/cards/9805158815

Also adds regression coverage for title-only and content-only document updates, and updates the Basecamp skill/docs to make the safer partial-update behavior explicit.

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Summary by cubic

Prevents data loss in basecamp files update for documents by preserving untouched title/content when only one field changes. Adds safe clears with empty flags and tightens validation (including autodetect vaults) to prevent invalid updates.

• Bug Fixes
  • Document updates use buildDocumentUpdateRequest to fetch and merge existing fields when only one flag is set, converting Markdown and resolving local images only when content changes.
  • Honors empty flags to clear fields by omitting them from the PUT body; detects whether --title/--content were set so no flags show a no-op message.
  • Validates updates by --type and in autodetect mode: rejects --content for vault/folder (including content-only updates when the ID resolves to a vault), requires a change for each type, and shows usage hints on invalid types; adds tests and updates help text and skills/basecamp/SKILL.md.

^{Written for commit 657e20d. Summary will update on new commits.}

[Copilot]

Pull request overview

This PR prevents data loss when running basecamp files update on documents by preserving the untouched title/content field during partial updates (because the underlying API behaves like a destructive PUT).

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Changes:

• Update document handling in files update to fetch the current document and merge fields for title-only/content-only updates.
• Add regression tests covering title-only and content-only document updates.
• Document the safer partial-update semantics in the Basecamp skill docs.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
internal/commands/files.go	Builds document update requests by merging existing fields to avoid clearing omitted title/content on PUT-style updates.
internal/commands/files_test.go	Adds tests that assert the request body preserves the untouched document field during partial updates.
skills/basecamp/SKILL.md	Updates examples and explicitly documents the CLI’s partial-update semantics for documents.

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[cubic-dev-ai]

No issues found across 3 files

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

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[cubic-dev-ai]

1 issue found across 3 files (changes from recent commits).

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="internal/commands/files.go">

<violation number="1" location="internal/commands/files.go:1223">
P2: Content-only updates without `--type` can auto-detect to vault and incorrectly send a vault title update with an empty/unset title instead of returning a usage error.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

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