feat: Expand AI agent branch prefixes and co-author email detection for Roo Code, Windsurf, and OpenHands

### Problem Statement
Currently, `disclosure` detects AI tool involvement from branch naming conventions (`KnownAgentBranchPrefixes`), committer bot emails (`KnownAgentCommitters`), and co-author trailer emails (`KnownCoAuthorEmails`).

However, several widely used AI coding agents and IDE tools are missing from these maps:
1. **Roo Code (Roo Cline)**: Uses branch prefixes `roo/` and `roo-code/`.
2. **Windsurf (Codeium)**: Uses branch prefix `windsurf/` and co-author email `noreply@windsurf.com`.
3. **OpenHands (OpenDevin)**: Uses branch prefix `openhands/` and `swe-agent/`.
4. **Continue.dev**: Uses co-author email `noreply@continue.dev`.

### Proposed Solution
1. Add `roo/`, `roo-code/`, `windsurf/`, `openhands/`, and `swe-agent/` to `KnownAgentBranchPrefixes` in `detection/constants.go`.
2. Add `noreply@continue.dev` and `noreply@windsurf.com` to `KnownCoAuthorEmails`.
3. Add unit test cases in `branchname_test.go` and `trailer_test.go` to maintain high test coverage.

Start in detection/constants.go to review KnownAgentBranchPrefixes and KnownCoAuthorEmails, then read branchname_test.go and trailer_test.go for existing table-driven cases. Run the relevant detection tests first; done means the listed branch prefixes and co-author emails are detected and the new cases pass.

Written by the indexing model from the issue text.