fix(v0.6.13): improve Context workflow recovery guidance

[qiansc]

Summary

• defer provisional code evidence validation until declared extraction phases are indexed
• clarify debug initialization for new and existing workspaces
• create and document .tmp/agent-payloads/ during initialization
• document downstream publication of completed Context outputs

Release

• published as Context 0.6.13
• all seven @c4a/*@0.6.13 packages are available on npm

Verification

• bun run build
• bun run verify:full
• bun run release:prepare
• npm pack dry-run for all published packages