feat(tri27): Staking Commands

[gHashTag]

Sub-Issue #441: Staking Commands

Files: src/tri27/stake_commands.zig (NEW, ~300 LOC)

Tasks:

• Create spec/stake_commands.tri
• Generate stake_commands.zig via tri gen
• Implement commands:
  • tri27 stake list
  • tri27 stake info
  • tri27 stake rewards
  • tri27 stake harvest
• Integrate with staking.zig
• Add lock period display (7-365 days)

Parent: #435