feat(dep): add --blocks shorthand flag for natural dependency syntax

[kraitsura]

Agents naturally try to use 'bd dep --blocks ' when establishing blocking relationships - a desire path revealing intuitive mental model for how dependencies should work.

Motivation

When AI agents set up dependency chains, they consistently attempt:
bd dep conduit-abc --blocks conduit-xyz

This reveals a desire path - the syntax users naturally reach for before reading documentation. Instead of fighting this intuition, we embrace it.

Changes

• Add --blocks (-b) flag to the bd dep command
• Support syntax: bd dep --blocks
• Equivalent to: bd dep add
• Full daemon and direct mode support
• Cycle detection and child-parent anti-pattern checks
• JSON output support for programmatic use

Backwards Compatibility

This is purely additive. The existing command structure remains:

• 'bd dep add' subcommand works exactly as before
• All other dep subcommands (remove, list, tree, cycles) unchanged
• No breaking changes to existing workflows

Examples

bd dep bd-xyz --blocks bd-abc # bd-xyz blocks bd-abc
bd dep bd-xyz -b bd-abc # Same, using shorthand
bd dep add bd-abc bd-xyz # Original syntax still works

Testing

• Added TestDepBlocksFlag for flag initialization
• Added TestDepBlocksFlagFunctionality for semantic correctness
• All existing tests pass

[steveyegge]

LGTM with the fix I pushed.

Fix applied: The daemon code path was returning early after AddDependency(), skipping the cycle detection that runs for direct mode. I restructured so both paths share the cycle detection and output code.

Note on CI: The lint failures are pre-existing baseline issues in unrelated files (gate.go, daemon_autostart.go, etc.) - not introduced by this PR. Those need a separate fix to the .golangci.yml exclusions.

Thanks for the contribution - this is a nice UX improvement for agents!

[steveyegge]

Merged via 6202711 after rebasing to resolve conflicts. Thanks @kraitsura!