v0.8.2 — branch/convert now verified against the real CLIs

Two bugs found by exercising every operation against the real agent CLIs, plus the harness that caught them.

Fixed

• Claude sessions branched or converted in workspaces with spaces (or dots, parentheses, non-ASCII letters) couldn't be resumed. showagent wrote them into a project directory the claude CLI never scans — it replaces every non-alphanumeric character with a dash, we only replaced path separators. Branch a session in ~/code/my project and claude --resume now just works. (#6-era bug, reported by a user — thanks!)
• Sessions converted into Gemini were undiscoverable (and undeletable) in the picker. The legacy sha256 project dir is one-way; we now claim it with gemini-cli's own .project_root marker so both gemini's migration and our discovery map it back to the workspace.

New

• scripts/e2e-real.sh: a real-CLI end-to-end matrix. Seeds tiny sessions with claude -p and codex exec (one workspace deliberately contains spaces), branches and converts them through showagent's own code paths, then verifies every artifact with the target CLI itself: claude --resume, codex exec resume, gemini --list-sessions, opencode export — and deletes everything through showagent afterwards. 22 checks, currently all green on claude + codex + gemini + opencode.

Full test suite, lint and 5-target cross-compile remain green.