fix(staging): avoid unnecessary daemon start and AWS fetch in edit/add commands

[mpyw]

Summary

• Implement "Ping-first" pattern in EditUseCase and AddUseCase to avoid unnecessary daemon auto-start and AWS requests
• Move Pinger/Starter interfaces from lifecycle package to store layer for correct dependency direction
• Update AgentStore interface to embed Pinger/Starter
• Add comprehensive unit tests for all Ping-first cases (97.9% coverage)

Problem

When editing or adding staged parameters, the edit command would auto-start the daemon and make unnecessary AWS requests even when nothing was staged. This was caused by GetEntry calls that auto-start the daemon.

Solution

Check if daemon is running (via Pinger.Ping()) before accessing staged state:

• If Ping fails → daemon not running → nothing staged → skip to AWS/default
• If Ping succeeds → daemon running → check staged state

This pattern is applied to:

• EditUseCase.Baseline() - Returns AWS value if daemon not running
• EditUseCase.Execute() - Skips staged check if daemon not running
• AddUseCase.Draft() - Returns "not staged" if daemon not running

Test plan

• All existing tests pass
• New Ping-first tests added for Edit and Add use cases
• Coverage: usecase/staging at 97.9%
• go build ./... succeeds
• go test ./... passes

Fixes #122

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.35%. Comparing base (6eb4e48) to head (69f1058).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #123      +/-   ##
==========================================
+ Coverage   90.29%   90.35%   +0.05%     
==========================================
  Files         132      132              
  Lines        7701     7745      +44     
==========================================
+ Hits         6954     6998      +44     
  Misses        503      503              
  Partials      244      244              

Flag	Coverage Δ
e2e	67.77% <1.96%> (-0.38%)	⬇️
platform-darwin	64.38% <ø> (ø)
platform-linux	62.85% <ø> (ø)
platform-windows	73.46% <ø> (ø)
unittests	79.69% <100.00%> (+0.11%)	⬆️

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