Pi: the source_repo collision guard has no escape hatch on the primary surface

[TheAmericanMaker]

Problem

#127 makes publishEntry refuse a publish whose source_repo differs from the one recorded on the entry's newest version, with allowSourceRepoChange (allow_source_repo_change on codecarto_publish) as the opt-out for a repository that genuinely moved.

That opt-out is MCP-only. /codecarto-publish is registered with handler: async (_args, ctx) (extensions/codecarto/index.ts:718) and takes no arguments, so a Pi user who trips the guard after a rename, org transfer, or host change cannot publish at all. The error surfaces through ctx.ui.notify(\Unable to publish: ${message}`, "error") (:781`) and the run ends there.

Pi is also where the guard is most likely to fire. slug and source_repo both derive from ctx.cwd (:745, :766), so two same-named directories under different parents collide by construction — see the sibling issue on using the git remote instead.

CLAUDE.md puts Pi first in surface priority ("New features land here first"). This one landed on MCP only. #127 flagged the inversion deliberately rather than riding it along in a bug fix, which is why this is filed separately.

As landed in #127, the refusal message no longer prescribes an action the caller may not expose — it names where each remedy lives instead. That keeps the message honest; it does not give Pi the remedy.

Proposed solution

Pi already calls ctx.ui.confirm for the publish preview (:760). The conflict looks like it belongs in the same place: catch the refusal, present the recorded vs. incoming source_repo, and offer the override as a second confirm rather than a flag the user has to know about.

A flag would also work and is closer to existing precedent — /codecarto-library-init already parses args.trim().split(/\s+/) for --namespace — but a blind --allow-source-repo-change on a command that otherwise takes no arguments is harder to discover at the moment it is needed.

Alternatives considered

• Leave it. A dead-end is still strictly better than the silent cross-project append it replaced, and the workaround (publish through MCP once) exists. It is a bad failure mode on the recommended surface, though.
• Auto-suffix the slug (-2, -3). docs/library-format.md promised this and it was never implemented; fix: refuse a publish that would append to another project's history #127 removed the promise rather than building it, on the grounds that silent suffixing is its own surprise for an agent-driven tool. Not revisiting that here.

Scope

• Template (.codecarto/)
• Pipeline definition / variant
• Pi extension
• MCP server
• Core (core/)
• Documentation
• CI / release

Additional context

Follows #127, which fixes #123. Sibling: the ctx.cwd-as-source_repo default.