feat(ci): unified build-notification action for Flex Slack alerts

.github/actions/build-notification/.gitignore

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+.DS_Store
+.idea
+*.log
+tmp/
+
+*.tern-port
+node_modules/
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+*.tsbuildinfo
+.npm
+.eslintcache

.github/actions/build-notification/.prettierignore

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+dist/
+node_modules/

.github/actions/build-notification/.prettierrc.js

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+'use strict'
+
+module.exports = {
+  printWidth: 80,
+  tabWidth: 2,
+  useTabs: false,
+  semi: false,
+  singleQuote: true,
+  jsxSingleQuote: false,
+  trailingComma: 'es5',
+  bracketSpacing: true,
+  jsxBracketSameLine: false,
+  arrowParens: 'avoid',
+  endOfLine: 'lf',
+}

.github/actions/build-notification/README.md

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+# Build Notification
+
+Single entrypoint for oe-core build Slack notifications. Workflows pass context and optionally a `notification_kind`; this action decides whether to send, the payload shape, and which webhook to use.
+
+## Usage
+
+Success notifications run inline in `run-build`:
+
+- **All builds** — `deployed` after artifact upload (tagged → `SLACK_WEBHOOK_ARTIFACTS_DEPLOY_URL_TAGGED`, branch → `SLACK_WEBHOOK_URL`)
+- **Tagged builds** — **Build's done!** (`cache-synced`) after S3 cache push via `SLACK_WEBHOOK_URL_TAGGED`
+
+Failure and cancelled notifications run from a separate job at the end of the build workflow.
+
+```yaml
+notify-build:
+  name: Notify Build Outcome
+  runs-on: ubuntu-latest
+  needs: [decide-refs, run-build]
+  if: always() && (needs.run-build.result == 'failure' || needs.run-build.result == 'cancelled')
+  steps:
+    - name: Fetch initial sources for action
+      uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
+      with:
+        submodules: false
+        path: ./oe-core-for-workflow
+    - name: Notify build outcome
+      uses: ./oe-core-for-workflow/.github/actions/build-notification
+      continue-on-error: true
+      with:
+        workflow: flex-build
+        notification_kind: auto
+        event_name: ${{ github.event_name }}
+        job_result: ${{ needs.run-build.result }}
+        webhook_url: ${{ secrets.SLACK_WEBHOOK_URL }}
+        webhook_url_tagged: ${{ vars.SLACK_WEBHOOK_URL_TAGGED }}
+        workflow_name: Build Flex image on github workflows
+        oe_core_ref: ${{ needs.decide-refs.outputs.oe-core }}
+        monorepo_ref: ${{ needs.decide-refs.outputs.monorepo }}
+        firmware_ref: ${{ needs.decide-refs.outputs.ot3-firmware }}
+        variant: ${{ needs.decide-refs.outputs.variant }}
+        console_url: ${{ needs.run-build.outputs.console_url }}
+        system_url: ${{ needs.run-build.outputs.system_url }}
+        fullimage_url: ${{ needs.run-build.outputs.fullimage_url }}
+        version_file_url: ${{ needs.run-build.outputs.version_file_url }}
+        release_notes_file_url: ${{ needs.run-build.outputs.release_notes_file_url }}
+```
+
+## Webhook routing (build-ot3-actions.yml)
+
+| Step | When | Branch builds | Tagged builds |
+| --- | --- | --- | --- |
+| Notify artifacts deployed | After S3 artifact upload | `SLACK_WEBHOOK_URL` | `SLACK_WEBHOOK_ARTIFACTS_DEPLOY_URL_TAGGED` |
+| Notify build complete | After S3 cache push | skip | `SLACK_WEBHOOK_URL_TAGGED` |
+| notify-build (failure/cancelled) | End of workflow | `SLACK_WEBHOOK_URL` | `SLACK_WEBHOOK_URL_TAGGED` |
+
+Each step passes the appropriate URL via `webhook_url` (branch) and `webhook_url_tagged` (tagged). The action picks based on whether `monorepo_ref` starts with `refs/tags/`.
+
+## Routing rules (`flex-build`)
+
+Set `notification_kind` to target a specific alert, or `auto` (default) to derive the kind from `job_result`.
+
+| Condition | Notification | Webhook target |
+| --- | --- | --- |
+| `event_name != workflow_dispatch` | skip | |
+| `notification_kind: deployed`, `job_result == success`, branch build | send `deployed` | `webhook_url` |
+| `notification_kind: deployed`, tagged build with non-empty `variant` | send `deployed` | `webhook_url_tagged` (fallback: `webhook_url`) |
+| `notification_kind: deployed`, tagged build with empty `variant` | skip | |
+| `notification_kind: cache-synced`, tagged build with non-empty `variant`, `job_result == success` | send `cache-synced` | `webhook_url_tagged` (fallback: `webhook_url`) |
+| `notification_kind: cache-synced`, branch build | skip | |
+| `notification_kind: auto`, `job_result == failure` | send `failure` | tagged or default by ref |
+| `notification_kind: auto`, `job_result == cancelled` | send `cancelled` | tagged or default by ref |
+| other combinations | skip | |
+
+## Slack Workflow setup
+
+Webhook URLs must be Slack Workflow trigger URLs (not legacy Incoming Webhooks).
+
+| GitHub config | Slack workflow |
+| --- | --- |
+| `secrets.SLACK_WEBHOOK_URL` | Branch builds — deployed, failure, cancelled |
+| `vars.SLACK_WEBHOOK_ARTIFACTS_DEPLOY_URL_TAGGED` | Tagged builds — artifacts available (`status: deployed`) |
+| `vars.SLACK_WEBHOOK_URL_TAGGED` | Tagged builds — **Build's done!** after cache sync (`status: cache-synced`), plus failure/cancelled |
+
+## Outputs
+
+| Output | Description |
+| --- | --- |
+| `sent` | `true` when a webhook POST was made |
+| `notification_kind` | `deployed`, `cache-synced`, `failure`, `cancelled`, or `none` |
+| `webhook_target` | `tagged`, `default`, or `none` |
+| `skip_reason` | Why a notification was skipped |

.github/actions/build-notification/action.yml

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+name: "Build Notification"
+description: "Single entrypoint for Flex build Slack notifications with routing rules."
+inputs:
+  workflow:
+    description: "Workflow rule set to apply (currently flex-build)."
+    required: true
+    default: "flex-build"
+  event_name:
+    description: "GitHub event name (for example workflow_dispatch)."
+    required: true
+  job_result:
+    description: "Job result: success, failure, cancelled, or skipped."
+    required: true
+  notification_kind:
+    description: "Notification to evaluate: auto (default), deployed, cache-synced, failure, or cancelled."
+    required: false
+    default: "auto"
+  webhook_url:
+    description: "Slack incoming webhook for branch builds and fallback."
+    required: false
+    default: ""
+  webhook_url_tagged:
+    description: "Slack workflow webhook for tagged builds. Falls back to webhook_url when empty."
+    required: false
+    default: ""
+  workflow_name:
+    description: "Human-readable workflow name for the Slack payload."
+    required: false
+    default: ""
+  workflow_run_url:
+    description: "Link to the workflow run. Defaults to the current run URL."
+    required: false
+    default: ""
+  failed_jobs:
+    description: "Comma-separated failed job names (optional)."
+    required: false
+    default: ""
+  oe_core_ref:
+    description: "oe-core ref."
+    required: false
+    default: ""
+  monorepo_ref:
+    description: "Monorepo ref."
+    required: false
+    default: ""
+  firmware_ref:
+    description: "Firmware ref."
+    required: false
+    default: ""
+  variant:
+    description: "Build variant from decide-refs (internal-release, release, or empty)."
+    required: false
+    default: ""
+  console_url:
+    description: "S3 console URL."
+    required: false
+    default: ""
+  system_url:
+    description: "System update zip URL."
+    required: false
+    default: ""
+  fullimage_url:
+    description: "Full image tar URL."
+    required: false
+    default: ""
+  version_file_url:
+    description: "Version file URL."
+    required: false
+    default: ""
+  release_notes_file_url:
+    description: "Release notes file URL."
+    required: false
+    default: ""
+  dry_run:
+    description: "When true, evaluate routing and build payload but do not POST."
+    required: false
+    default: "false"
+outputs:
+  sent:
+    description: "true when a Slack notification was sent, false when skipped."
+  notification_kind:
+    description: "deployed, cache-synced, failure, cancelled, or none."
+  webhook_target:
+    description: "tagged, default, or none."
+  skip_reason:
+    description: "Why the notification was skipped, empty when sent."
+runs:
+  using: "node24"
+  main: "dist/index.js"