feat(docs): enhance README and build pipeline rules for clarity

- update README to clarify the exclusion of bulk artifacts from git
- specify committed curated results subset in README and rules
- improve descriptions of output directories and their contents
- refine details on the pipeline's data generation and reporting processes

docs/rules/build-pipeline-tasks.md

@@ -31,10 +31,14 @@ out/
 - Tasks communicate exclusively through these artifacts - never through
   shared in-process state
   (see [code-python-style.md](code-python-style.md)).
-- **`./out/` is git-ignored** (except nothing - the whole tree). Sources
-  of truth are the specs, the rules, and the code; artifacts are
-  reproducible from them ([data-determinism.md](data-determinism.md)).
-  Never commit generated artifacts "for convenience".
+- **The bulk of `./out/` is git-ignored.** Sources of truth are the
+  specs, the rules, and the code; artifacts are reproducible from them
+  ([data-determinism.md](data-determinism.md)). A curated results subset
+  IS committed (owner decision, 2026-07-11): `out/report/` (REPORT.md,
+  charts, tables, diagrams), `out/config/` (lab_config.yaml,
+  hw_prices.yaml), and the `out/.done/` markers - exactly the exceptions
+  listed in `.gitignore`. Never commit the bulk artifacts (corpus,
+  databases, stores, archives, raw benchmark data) "for convenience".
 
 ## 2. Completion markers
 
@@ -92,7 +96,9 @@ out/
 
 - **Writing an artifact outside `./out/`** or a task writing into another
   task's output directory.
-- **Committing `./out/` content to git.**
+- **Committing bulk `./out/` content to git** (corpus, databases, stores,
+  archives, raw benchmark data) - only the curated subset in `.gitignore`
+  (`report/`, `config/`, `.done/`) is committed.
 - **A marker written on partial success** - see
   [code-error-handling.md](code-error-handling.md).
 - **Running benchmarks while converters are still running.**