squad watch --board fails for org-owned ProjectV2 (always uses --owner @me) #1079

Summary: The --board capability hardcodes --owner @me when calling gh project item-list and there is no flag or config option to override it. Users whose project board is org-owned (e.g. https://github.com/orgs/<org>/projects/22) cannot use --board at all.

Repro:

1. Have access only to org-owned ProjectV2 boards (no personal @me projects). Verify with gh project list --owner @me returning "No projects found for @me".
2. Run squad watch --board --board-project 22 (or any non-@me project number) in a squad repo.
3. Observe in stderr / round summary:

   board: board error: Command failed: gh project item-list 22 --owner @me --format json --limit 300
   GraphQL: Could not resolve to a ProjectV2 with the number 22. (viewer.projectV2)
   

Root cause: packages/squad-cli/src/cli/commands/watch/capabilities/board.ts hardcodes '--owner', '@me' in two places (the BoardCapability.execute method and in updateBoardStatus). There is no CLI flag or .squad/config.json field to override it.

Proposed fix:

1. Read owner from the capability config (context.config['owner']), defaulting to '@me'.
2. Add a --board-owner <name> CLI flag in cli-entry.ts to set capabilities.board.owner.
3. Update help text/flag logic to allow this new flag and default to @me.

Tests to add:

• BoardCapability: supplied owner config is used in item-list command.
• CLI: new flag parses and composes with other board flags.

Docs to update:

• CLI/README: Document new flag and config pattern under board lifecycle features.

Workaround:
Users may patch the package locally until this lands (see handoff doc in .squad/patches/UPSTREAM-HANDOFF.md for context).

Environment:

• OS: Windows 11 (also repros on Linux/macOS)
• Node: 18+
• CLI: Any gh with org ProjectV2 access