Mark auto-generated files for GitHub linguist (databricks#5269)

## Changes

Extend `linguist-generated=true` coverage so generated files don't
pollute language stats or show up as hand-written code in review.
Follows the existing convention of one local `.gitattributes` per
generated folder (alongside `bundle/schema/`, `bundle/internal/tf/`,
`bundle/internal/validation/generated/`, `acceptance/`, `integration/`).

New / updated local files:

| Generator | `.gitattributes` location | Pattern |
|---|---|---|
| `./task generate-direct` | `bundle/direct/dresources/` |
`*.generated.yml` |
| `./task generate-schema-docs` | `bundle/schema/` (extended) |
`jsonschema_for_docs.json` |
| `./task generate-schema` | `bundle/internal/schema/` |
`annotations_openapi.yml` |
| `./task generate-docs` | `bundle/docsgen/output/` | `*.md` |
| `mockery` | `internal/mocks/` | `*.go` |
| `./task pydabs-codegen` | `python/databricks/bundles/` |
`{catalogs,jobs,pipelines,schemas,volumes}/**` |

Excluded by request from review:
- `internal/genkit/tagging.py{,.lock}` and
`.github/workflows/tagging.yml` — kept visible because changes there can
affect the release process (@andrewnester).
- `acceptance/**/out*` and `acceptance/**/output/**` — kept visible
because acceptance-output diffs are how reviewers detect behavior
changes (@pietern, @andrewnester).

## Why

`bundle/direct/dresources/apitypes.generated.yml` (and
`resources.generated.yml`) were showing up as human-authored code on
GitHub. The genkit-managed section of the root `.gitattributes` only
covers `cmd/account/**` and `cmd/workspace/**`, so the rest of the
auto-generated tree was unmarked. This brings linguist's view in line
with `.agent/rules/auto-generated-files.md`.

## Tests

Verified each pattern with `git check-attr linguist-generated <path>`:
- Intended generated files resolve to `true`.
- Adjacent manually-maintained files stay `unspecified`:
`bundle/direct/dresources/apitypes.yml`,
`bundle/internal/schema/annotations.yml`,
`bundle/internal/schema/annotations_openapi_overrides.yml`,
`bundle/docsgen/{main.go,README.md}`, `bundle/schema/schema.go`,
`internal/mocks/README.md`,
`python/databricks/bundles/{__init__.py,build.py,core/**}`.
- Pre-existing local `.gitattributes` files (TF schema, validation
generated, `bundle/schema/jsonschema.json`, acceptance `out.test.toml`)
still resolve correctly.

`./task ws` passes.

_This PR was written by Claude Code._

Author: janniklasrose

bundle/direct/dresources/.gitattributes

@@ -0,0 +1 @@
+*.generated.yml linguist-generated=true

bundle/docsgen/output/.gitattributes

@@ -0,0 +1 @@
+*.md linguist-generated=true

bundle/internal/schema/.gitattributes

@@ -0,0 +1 @@
+annotations_openapi.yml linguist-generated=true

bundle/schema/.gitattributes

@@ -1 +1,2 @@
 jsonschema.json linguist-generated=true
+jsonschema_for_docs.json linguist-generated=true

internal/mocks/.gitattributes

@@ -0,0 +1 @@
+*.go linguist-generated=true

python/databricks/bundles/.gitattributes

@@ -0,0 +1,5 @@
+catalogs/** linguist-generated=true
+jobs/** linguist-generated=true
+pipelines/** linguist-generated=true
+schemas/** linguist-generated=true
+volumes/** linguist-generated=true