Add anthropics/buffa-packaging plugin v0.3.0

protoc-gen-buffa-packaging emits a mod.rs module tree that includes
per-file output from protoc-gen-buffa (or any plugin layered on it).
The plugin reads the proto package structure (not message bodies) and
writes a mod.rs that include!s each generated file at the right module
nesting level.

Requires `strategy: all` so the plugin sees the full file set in one
invocation. Supports a `filter=services` option for packaging output
from service-stub generators that skip files without services.

Crates: https://crates.io/crates/protoc-gen-buffa-packaging
Repo: https://github.com/anthropics/buffa

Author: iainmcgin

plugins/anthropics/buffa-packaging/source.yaml

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+source:
+  crates:
+    crate_name: protoc-gen-buffa-packaging

plugins/anthropics/buffa-packaging/v0.3.0/.dockerignore

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+*
+!Dockerfile

plugins/anthropics/buffa-packaging/v0.3.0/Dockerfile

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+# syntax=docker/dockerfile:1.19
+FROM rust:1.91.1-alpine3.22 AS builder
+RUN apk add --no-cache musl-dev
+WORKDIR /app
+ENV CARGO_REGISTRIES_CRATES_IO_PROTOCOL=sparse
+RUN --mount=type=cache,target=/usr/local/cargo/registry,sharing=locked --mount=type=cache,target=/root/target \
+    cargo install protoc-gen-buffa-packaging --version 0.3.0 --locked --root /app
+
+FROM gcr.io/distroless/static-debian12:latest@sha256:87bce11be0af225e4ca761c40babb06d6d559f5767fbf7dc3c47f0f1a466b92c AS base
+
+FROM scratch
+COPY --link --from=base / /
+COPY --link --from=builder /app/bin/protoc-gen-buffa-packaging /protoc-gen-buffa-packaging
+USER nobody
+ENTRYPOINT ["/protoc-gen-buffa-packaging"]

plugins/anthropics/buffa-packaging/v0.3.0/buf.plugin.yaml

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+version: v1
+name: buf.build/anthropics/buffa-packaging
+plugin_version: v0.3.0
+source_url: https://github.com/anthropics/buffa
+description: Emits a mod.rs module tree that includes per-file output from protoc-gen-buffa (and plugins layered on it). Run with strategy=all so the plugin sees the full file set in one invocation.
+output_languages:
+  - rust
+spdx_license_id: Apache-2.0
+license_url: https://github.com/anthropics/buffa/blob/v0.3.0/LICENSE