Source upgrade: current main does not compile in prepare_source_workspace_for_upgrade

[chubes4]

Summary

homeboy upgrade --method source cannot install current main because Homeboy fails to compile.

Reproduction

1. Create a clean worktree at current origin/main (762bcd004e945662a47b335e355573a4129509bd).
2. Run:

homeboy upgrade --method source --source-path /path/to/homeboy --force --skip-extensions --skip-runners

3. Observe Rust compilation fail:

error[E0308]: mismatched types
   --> src/core/upgrade/execution.rs:592:67
592 | fn prepare_source_workspace_for_upgrade(workspace_root: &Path) -> Result<()> {
    |                                                                   ^^^^^^^^^^ expected `Result<(), Error>`, found `()`

Expected

The accepted main source builds and the supported source-upgrade workflow completes.

Actual

The source-upgrade workflow stops before replacing the active binary. The existing installed binary remains unchanged (0.281.20+ef8a2c4863df).

Context

This blocks deployment preflight that requires the accepted fixes in Homeboy #7851, #7866, and #7867.

AI assistance

• AI assistance: Yes
• Tool(s): openai/gpt-5.6-terra and OpenCode
• Used for: Reproduced the supported source-upgrade workflow and drafted this report.