Add dependency flags to tq issue update

[version-1]

Add dependency flags to tq issue update

Summary

This PR adds CLI support for replacing or clearing issue dependencies through tq issue update, matching the existing PATCH /api/v1/issues/{id} dependency_ids contract.

主な変更点:

• Add --dependency <comma-separated-ids> to fully replace issue dependencies.
• Add --clear-dependencies to explicitly clear dependencies.
• Preserve existing specified-field-only update payloads with a typed CLI patch struct.
• Document the new flags in English and Japanese CLI references.

チケットへのリンク

Issue #45

やったこと

• tq issue update now rejects simultaneous --dependency and --clear-dependencies.
• --dependency "", non-integer IDs, zero/negative IDs, and duplicate IDs are usage errors.
• API validation errors, such as dependency cycles, continue to propagate to CLI stderr.
• Added CLI tests for replacement, clearing, usage errors, explicit --clear-dependencies=false, and server validation errors.

動作確認

• go test ./internal/cli/tq
• go test ./internal/cli/tq ./internal/issue/...
• go test ./internal/... ./cmd/issue-tracker ./cmd/orchestrator ./cmd/tq ./cmd/tasq-tui ./db/migrations
• git diff --check
• PR前レビュー: High 以上の指摘なし

レビュー & 動作確認 チェックリスト

• Dependency replacement - --dependency 1,2 sends dependency_ids: [1,2] and replaces the full dependency set.
• Dependency clearing - --clear-dependencies sends dependency_ids: [].
• Usage errors - conflicting flags and invalid dependency input exit as usage errors.
• Server validation propagation - server-side dependency validation messages are shown by the CLI.

推奨テスト計画:

1. Run tq issue update <id> --dependency <dep-id> against local issue-tracker and confirm the issue response contains the dependency.
2. Run tq issue update <id> --clear-dependencies and confirm dependencies are empty.
3. Try a cycle-producing dependency update and confirm the CLI prints the server validation error.

その他気になることや相談ごと

go test ./... was also attempted, but cmd/web fails during setup because cmd/web/frontend/dist is not present in this worktree. The non-web Go package set above passed.