feat: add required cache-key input, native GC, and server-driven config for v2 (#108)

* feat: add required cache-key input for v2

Replace the hardcoded GITHUB_REPO_NAME sticky disk key with a required
cache-key input. Users must explicitly declare which cache entity their
build targets, preventing cache thrashing in multi-target repos.

The cache-key is saved to action state and passed through to the commit
phase so the same key is used for both expose and commit RPCs.

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* feat: replace manual pruning with buildkit native gc

Remove max-cache-size-mb input and manual buildctl prune from the post
phase. Enable BuildKit's native garbage collection with a time-based
policy (keepDuration=192h / 8 days). Layers unused for longer than the
retention period are automatically cleaned up; active layers survive
indefinitely regardless of total cache size.

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* feat: add server-driven config infrastructure for GC and pre-commit hooks

Add BuildkitdConfig and PreCommitHook interfaces (server-config.ts) that
define the contract for server-driven cache lifecycle management. The
action reads BuildkitdConfig from the GetStickyDisk RPC response (with
hardcoded fallback for Phase 1) and runs pre-commit hooks from the
PrepareCommit RPC response before committing.

Refactor writeBuildkitdTomlFile to accept a BuildkitdConfig parameter
instead of hardcoding GC policy values. This makes it trivial to switch
from hardcoded defaults to server-provided config when the proto is
updated (Phase 2).

Add runPreCommitHooks dispatcher that executes an ordered list of opaque
shell commands with timeout and failure mode handling. The commit flow
now goes through prepareCommit -> runHooks -> conditionalCommit, with
Phase 1 returning unconditional commit + empty hooks.

Phase 1 (now): hardcoded gc=true, keepDuration=192h, no hooks
Phase 2: server returns BuildkitdConfig in GetStickyDiskResponse
Phase 3: server returns hooks via PrepareCommit RPC

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* chore: remove unused rollup build artifacts

Remove rollup.config.js and rollup devDependencies (@rollup/plugin-node-resolve,
@rollup/plugin-typescript, rollup). The repo switched to ncc for bundling in
commit 2ffcb3d; rollup artifacts were never cleaned up. The dist/main.bundle.mjs
file was already deleted in a prior commit.

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

---------

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

Author: piob-io

action.yml

@@ -5,6 +5,13 @@ branding:
   icon: layers
   color: black
 inputs:
+  cache-key:
+    description: >-
+      Unique identifier for this build's Docker layer cache. Builds with the
+      same cache-key share cached layers across runs. Set this to the Dockerfile
+      being built (e.g., services/api/Dockerfile). Jobs building different
+      Dockerfiles should use different cache-keys to avoid cache thrashing.
+    required: true
   buildx-version:
     description: Buildx version. (e.g., v0.23.0, latest)
     required: false
@@ -32,9 +39,6 @@ inputs:
   max-parallelism:
     description: "Maximum number of concurrent BuildKit RUN steps. Defaults to the number of vCPUs on the runner."
     required: false
-  max-cache-size-mb:
-    description: "Amount of build cache to retain after pruning, in MB (e.g., 409600 for 400GB). If not set, pruning is skipped."
-    required: false
 runs:
   using: node24
   main: dist/index.js