Improve error handling and diagnostics for the audita subprocess

architecture.md

@@ -132,7 +132,7 @@ Audita config keys:
 
 - `pipeline.audita.binary` (required)
 - `pipeline.audita.timeout` (default: `3h`)
-- `pipeline.audita.llm_api_key_env` (optional; default: `AUDITA_LLM_API_KEY`)
+- `pipeline.audita.llm_api_key_env` (optional; no automatic default)
 - `pipeline.audita.modules` (default sequence: `glossary,homophones,glossary,spoken_word,grammar,homophones,glossary`)
 - `pipeline.audita.base_url` (default: `https://openrouter.ai/api/v1`)
 - `pipeline.audita.model` (default: `openrouter/google/gemma-4-31b-it`)
@@ -145,7 +145,8 @@ Audita secret-handling policy:
 
 - `llm_api_key_env` stores only the environment variable **name**.
 - API key values are read from the process environment at runtime and are not stored in `pipeline.yml`, manifest metadata, generated configs, or logs.
-- If the named env var is missing/empty, the Audita adapter omits `AUDITA_LLM_API_KEY` from subprocess env overrides and continues.
+- If `llm_api_key_env` is configured and the named env var is missing/empty, the Audita adapter fails before invocation with a redacted error.
+- If `llm_api_key_env` is empty/omitted, the Audita adapter omits `AUDITA_LLM_API_KEY` from subprocess env overrides and continues.
 
 Validation currently enforces:
 
@@ -331,6 +332,7 @@ All adapters currently have fake/no-op implementations for tests/scaffold execut
 
 - Context cancellation + optional timeout.
 - Explicit executable/args, working dir, env overrides.
+- Parent environment inheritance with override merge semantics (override values win).
 - Stdout/stderr log file handling.
 - Exit code and timing capture.
 - Actionable error wrapping.