# RetrieX Patch 9.0e - PromptBuilder Fact-Grounding YAML-only

## Scope

This patch builds on Patch 9.0d.

It only migrates the PromptBuilder fact-grounding rule group to YAML-only accessors:

- `sections.fact_grounding_rules_label`
- `fact_grounding.base_rules`
- `fact_grounding.with_shop_rules`
- `fact_grounding.without_shop_rules`
- `fact_grounding.technical_rules`

## Included changes

- `src/Config/PromptBuilderConfig.php`
  - Removes PHP fallback accessors for the fact-grounding section label and fact-grounding rule lists.
  - Uses required YAML accessors for the migrated paths.

- `config/retriex/prompt.yaml`
  - Adds two fact-grounding base rules that still existed as PHP fallback text but were not present in YAML.

## Not changed

This patch does not change:

- Measurement evidence guard logic
- Role guard keywords
- Technical product keywords
- Accessory request keywords
- Retrieval
- Commerce
- Shop matching
- AgentRunner
- Frontend/SSE behavior

## Validation

Run after applying:

```bash
php bin/console cache:clear
php bin/console mto:agent:config:validate
php bin/console mto:agent:config:audit-source --details
php bin/console mto:agent:regression:test
```

Expected result:

- Configuration validation remains OK.
- Regression baseline remains OK.
- PromptBuilderConfig fallback accessors for `fact_grounding.*` disappear from the audit.
