fix(sandbox): round 7 align spawn evidence

docs/core-data-structures/sandbox.md

@@ -139,10 +139,10 @@ interface ConfinedArgv {
 }
 ```
 
-The operator-facing local-provider key remains `runnerFailureSignatures`: an operator-configured runner must supply at least one non-empty, single-line, case-insensitive substring for its own pre-exec refusal dialect. The provider maps those entries into one rule. Consumers directly spawn `ConfinedArgv.argv`, so a missing, non-executable, or unloadable runner — including a script whose shebang interpreter is unavailable — rejects through the spawn channel rather than a stderr rule; after a process starts, child exits such as 126 or 127 remain ordinary unless the selected runner's documented fatal signature matches.
+The operator-facing local-provider key remains `runnerFailureSignatures`: an operator-configured runner must supply at least one non-empty, single-line, case-insensitive substring for its own pre-exec refusal dialect. The provider maps those entries into one rule. Consumers directly spawn `ConfinedArgv.argv`, so a missing runner, a non-executable runner, or an executable script whose shebang interpreter is unavailable rejects through the spawn channel rather than a stderr rule when Node supplies attributable `ENOENT`/`EACCES` evidence; after a process starts, child exits such as 126 or 127 remain ordinary unless the selected runner's documented fatal signature matches.
 
 ## Provider and fail-closed errors
 
-`ctx.sandbox.confine(argv, policy)` returns a `ConfinedArgv` or throws `SandboxUnavailableError` with code `SANDBOX_UNAVAILABLE` when no usable backend exists. Any direct spawn rejection of the returned argv proves the confined launch never started, but only an executable-class error with Node spawn provenance for provider argv[0] after the caller-owned workdir is independently verified usable carries infrastructure meaning and the original error as detail. Invalid or unusable workdirs, resource failures, unrelated syscalls, and unstructured rejections retain the consumer's ordinary command-start semantics. After a process starts, a matching structured rule identifies a runner refusal. Silent unconfined passthrough is never legal for a confined policy.
+`ctx.sandbox.confine(argv, policy)` returns a `ConfinedArgv` or throws `SandboxUnavailableError` with code `SANDBOX_UNAVAILABLE` when no usable backend exists. Any direct spawn rejection of the returned argv proves the confined launch never started, but only `ENOENT` or `EACCES` with positive Node provenance for provider argv[0] after the caller-owned workdir is independently verified usable carries infrastructure meaning and the original error as detail. A bare `syscall: 'spawn'` without an exact error path, any other code, an invalid or unusable workdir, a resource failure, an unrelated syscall, or an unstructured rejection retains the consumer's ordinary command-start semantics. After a process starts, a matching structured rule identifies a runner refusal. Silent unconfined passthrough is never legal for a confined policy.
 
 Provider probing arbitrates between multiple candidates and is cached for the provider lifetime. A platform with one candidate may select it directly; execution-time refusal retains the safety property. The local provider reports bwrap and Seatbelt as full and preserves the Landlock launcher's full/partial kernel verdict.