Copilot App inconsistently discovers CLI sessions

## Description

Not all CLI sessions appear in the Copilot App. Two sessions with identical metadata (both have git repos, ADO host, valid branches, checkpoints) show different behavior — one loads, the other doesn't.

## Details

**Session that loaded:** `Org/Repo-A`, CWD `Q:\src\repo-a`, branch `user/myuser/feature-branch`
**Session that didn't:** `Org/Repo-B`, CWD `Q:\src\repo-b`, branch `main`

Both sessions have:
- Valid git repositories
- ADO host type
- Multiple turns and checkpoints
- Recent `updated_at` timestamps

Additionally, sessions started in non-git directories (e.g., agent-launched sessions with `repository: None`) are **never** discovered, even when the exact CWD is added to the app.

## Expected Behavior

All CLI sessions should be discoverable in the Copilot App, either by repo match or CWD match, regardless of:
- Whether the directory is a git repo
- Which branch the session was on
- The host type

## Steps to Reproduce

1. Start two Copilot CLI sessions in different git repos
2. Open the Copilot App and add both repo directories
3. Observe that only one session appears

For non-git sessions:
1. Start a Copilot CLI session in a non-git directory (e.g., an agent workspace)
2. Add that directory in the Copilot App
3. Session does not appear (`repository: None` in `session-store.db`)

## Environment

- **App version:** v0.2.30
- **OS:** Windows 11
- **Session store:** `~/.copilot/session-store.db`

Start by inspecting the Copilot App's session-discovery logic and how it reads ~/.copilot/session-store.db, then reproduce the mismatch with the two Windows repository sessions. Trace repo, CWD, branch, and host matching, including entries with repository: None. Done means matching sessions consistently appear when their repository or CWD is added, with coverage for git and non-git directories.

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