* feat: dsdgen compatibility

* chore: Use pre-generated C data files, unify comparison scripts (#257)

* chore: Use pre-generated C data files, unify comparison scripts

* chore: make scripts self-documenting; collapse scripts/README

Move per-script docs (usage, flags, env vars, output, exit codes) into the
top-of-file header comment of each script. The README's `## Scripts`
section becomes a one-line-per-script roadmap pointing readers at the
script files for details.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* chore: fold bootstrap-c.sh into generate-fixtures.sh; centralize usage in print_usage()

- Add `--compat trino|c` to generate-fixtures.sh:
  - `--compat trino` (default): existing Java generation behavior.
  - `--compat c`: download alamb/tpcds-data sfN with `git clone --depth 1`
    and extract into tests/fixtures/scale-N-c/. Supports `--rebuild` and
    `--verify`. Replaces bootstrap-c.sh, which is removed.
- Per-script header is now a one-liner + "see print_usage() below for
  details"; print_usage() sits immediately after the header with the
  full usage block (flags, env vars, examples, exit codes). Renamed
  `usage` -> `print_usage` everywhere.
- Update tpcdsgen/README.md, scripts/README.md, and the CI workflow
  (`tpcdsgen-conformance.yml`) to call generate-fixtures.sh --compat c
  instead of bootstrap-c.sh.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* ci: only run tpcdsgen conformance on tpcdsgen/ or .github/ changes

Adds a `paths` filter to both the push and pull_request triggers so the
suite no longer fires for unrelated changes (e.g. tpchgen-* edits, doc
tweaks at the repo root).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* refactor: rename return_reasons.dst to return_reasons_trino.dst

Pair the inherited Java/Trino distribution with the corrected C variant
so both filenames advertise their compat mode at a glance:

    return_reasons_trino.dst   <-- old return_reasons.dst (carries the
                                   "reason 30 missing, reason 31
                                   duplicated" bug, kept for byte-for-byte
                                   Trino fixture stability)
    return_reasons_c.dst       <-- corrected, used by --compat c

Updates the embedded_data.rs lookup table, the distribution loader,
and the doc-comment references in scaling.rs.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* chore: consolidate MD5SUMS into scale-N-{java,c}/ fixture dirs

Move the canonical Java reference hashes from
  tests/fixtures/java/scale-{1,10}/MD5SUMS
to
  tests/fixtures/scale-{1,10}-java/MD5SUMS

and generate a fresh
  tests/fixtures/scale-1-c/MD5SUMS

from the current alamb/tpcds-data sf1 download (post-regeneration).

The old tests/fixtures/rust/scale-{1,10}/MD5SUMS files are removed:
they were byte-identical to the Java set apart from dbgen_version, which
contains a generation timestamp and is always excluded from comparison.

The empty tests/fixtures/java/ parent directory is gone too.

README references already use the new scale-N-java/ paths (from
the earlier rename); no further doc updates were needed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* refactor: use 'trino' (not 'java') consistently for the Trino TPC-DS port

'java' is ambiguous — there may be multiple Java TPC-DS implementations.
The reference we target is specifically the Trino library, so name
everything after it for clarity:

  - tests/fixtures/scale-N-java/   -> tests/fixtures/scale-N-trino/
  - scripts/bootstrap-java.sh       -> scripts/bootstrap-trino.sh
  - TPCDS_JAVA_REPO  env var        -> TPCDS_TRINO_REPO
  - JAVA_DIR / JAVA_REPO_URL vars   -> TRINO_DIR / TRINO_REPO_URL
  - find_java_jar / clone_java_repo / build_java / test_java
        -> find_trino_jar / clone_trino_repo / build_trino / test_trino
  - CI artifact `test-fixtures-java` -> `test-fixtures-trino`
  - "Java fixture" log labels        -> "Trino fixture"
  - Doc references throughout READMEs and script headers updated.

Kept as-is: `actions/setup-java@v5`, `Java 11+` requirement, `java -jar`
/ `java -version` invocations, and `mvn`/`openjdk` references — those
refer to the Java language/runtime, not the Trino implementation.

The CLI flag and Rust `CompatMode::Trino` were already named `trino`;
this commit aligns the rest of the codebase.

Verified: `./scripts/test-all-tables.sh` passes 24/24 vs Trino, and
`./scripts/test-all-tables.sh --compat c` passes 23/23 vs C dsdgen
(customer.dat still skipped pending alamb/tpcds-data regeneration).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix: add references to documented bugs

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Co-authored-by: Andrew Lamb <andrew@nerdnetworks.org>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>