fix: keep managed Homeboy upgrades service-owned

[chubes4]

Why

Root-provisioned Homeboy at /usr/local/bin cannot replace itself when the agent runs as an unprivileged service user. This is the Homeboy executable recurrence of #203 and the same installation-ownership pattern previously repaired for Kimaki in #580.

Change

• Managed non-root setup and upgrade seed Homeboy into the configured service home and converge ownership of the executable and its two parent directories, including when the executable already exists. Existing service-user binaries are preserved.
• Homeboy integration commands run as the service identity with the service-owned bin first on PATH. AGENTS guidance also considers the service binary while preserving the compose-identity reachability gate from fix: bake a compose-reachable homeboy path into AGENTS.md guidance #639.
• Root, local, and external WordPress modes retain their prior install resolution.

Verification

Homeboy Cook retry-0a94a366-1862-563f-acaf-3ae08b6dd323 applied the candidate and recorded three passing gates (homeboy-components, homeboy-verification-guidance, service-identity-adoption); Homeboy publication refused its own green Lab provider lineage (homeboy#15115). Direct OpenCode Luna reviewed the isolated candidate and added ownership/path checks. Locally passed: homeboy-service-identity, homeboy-components, homeboy-verification-guidance, service-identity-adoption, integration-adapters, homeboy-project-id, agents-md-composition-integration, bash -n for touched scripts, and git diff --check. The full agents-md-guidance shell fixture reaches later assertions on macOS then loses Homebrew PHP and /sbin/md5 when it narrows PATH to /usr/bin:/bin; Linux CI is authoritative for that fixture.

Operational evidence

On the managed host the service-owned Homeboy 0.394.0 executable and matching daemon were verified before this PR; generated guidance still points at the compose-visible system binary until this integration upgrade is deployed and recomposed. Finalization occurred outside Homeboy after the repeated publication blocker; no credentials or host state are in the branch.

AI assistance: OpenAI gpt-6-sol via OpenCode diagnosed the VPS ownership mismatch and directed the tracked workflow; OpenAI gpt-6-luna via direct OpenCode refined code and tests in the issue-linked isolated worktree at Chris Huber’s direction. Chris reviewed the fallback scope.