docs: move execa Agent Note to implemented; update inbound links and README contracts

- proposed/testing -> implemented/testing with the lifecycle rewrite
  (Proposal->Decision in present tense, Acceptance criteria + Risks
  folded into Consequences); zh counterpart mirrored and both pairs
  re-recorded.
- the rejected NIH-audit roll-up pair now links the implemented/ path.
- loader-smoke README: captured output is bounded by execa's default
  100 MB maxBuffer, no longer unbounded.
- acp-snapshot README: harness.ts now also imports vitest (vi.waitFor),
  so the vitest-run-only constraint names both modules.
- jsonrpc keyless smoke: raise the invalid-env case's subprocess
  deadline to 25s (the 9s pick starved a cold tsx boot on slow NFS).

examples/jsonrpc-agent/tests/keyless-smoke.e2e.ts

@@ -176,7 +176,7 @@ describe('jsonrpc-agent keyless smoke', () => {
         DSH_MAX_TOKENS_AS_SUCCESS: 'sometimes',
       },
       stdin: 'ignore',
-      timeout: 9_000,
+      timeout: 25_000,
       killSignal: 'SIGKILL',
       reject: false,
     })
@@ -184,5 +184,5 @@ describe('jsonrpc-agent keyless smoke', () => {
     expect(exitCode, stderr).toBe(1)
     expect(stdout).toBe('')
     expect(stderr).toContain('plugin(s) failed to load: @deepseek-ai/dsh-jsonrpc')
-  }, 10_000)
+  }, 30_000)
 })