Add webhook subscription list command

[HunterCML]

Closes #205.
Part of #133.

What changed

• Adds sh1pt config webhooks sub list so event subscriptions have the same inspectable list path as webhook targets.
• Supports --json for automation with a stable { subscriptions: [] } shape while the backing store is still stubbed.
• Documents the command in the README webhook examples and the docs page.

Verification

• pnpm exec vitest run packages/cli/src/commands/config.test.ts
• pnpm --filter @profullstack/sh1pt typecheck
• pnpm --filter sh1pt-dot-com build
• git diff --check

[github-actions]

🤖 Auto-rebase: The branch was rebased successfully locally but could not be pushed to the fork. Please enable 'Allow edits from maintainers' in the PR settings, or rebase manually: git fetch upstream master && git rebase upstream/master.

[github-actions]

🤖 Auto-rebase: The branch was rebased successfully locally but could not be pushed to the fork. Please enable 'Allow edits from maintainers' in the PR settings, or rebase manually: git fetch upstream master && git rebase upstream/master.

[github-actions]

🤖 Auto-rebase: The branch was rebased successfully locally but could not be pushed to the fork. Please enable 'Allow edits from maintainers' in the PR settings, or rebase manually: git fetch upstream master && git rebase upstream/master.

[github-actions]

🤖 Auto-rebase: The branch was rebased successfully locally but could not be pushed to the fork. Please enable 'Allow edits from maintainers' in the PR settings, or rebase manually: git fetch upstream master && git rebase upstream/master.