docs(openspec): add harden-opencode-runtime-integration spec.md

Author: loong10k

openspec/changes/harden-opencode-runtime-integration/specs/server-lifecycle/spec.md

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+# Delta for Server Lifecycle
+
+## ADDED Requirements
+
+### Requirement: Long-running OpenCode processes use managed lifecycle semantics
+
+The SDK MUST provide a managed process abstraction for long-running OpenCode launch modes instead of applying the ordinary short-command timeout.
+
+#### Scenario: Web process remains alive
+
+- GIVEN a caller starts OpenCode Web through the managed API
+- WHEN startup succeeds
+- THEN the process MUST remain alive beyond the short-command timeout
+- UNTIL the caller stops it, the process exits, or an explicit lifetime policy terminates it
+
+### Requirement: Readiness is distinct from process spawn
+
+The SDK MUST expose readiness independently from successful process creation.
+
+#### Scenario: Process starts but health endpoint is unavailable
+
+- GIVEN the child process was spawned
+- AND the expected OpenCode HTTP endpoint does not become healthy before startup timeout
+- WHEN the caller awaits readiness
+- THEN readiness MUST fail
+- AND the process MUST be cleaned up according to the startup-failure policy
+
+### Requirement: Managed processes expose deterministic shutdown
+
+The SDK MUST provide graceful stop and force-kill operations with observable exit completion.
+
+#### Scenario: Graceful stop times out
+
+- GIVEN a managed process does not exit after a graceful stop request
+- WHEN the graceful shutdown timeout elapses
+- THEN the caller MUST be able to force terminate the process
+- AND the final exit state MUST be observable