Add shared agent instructions

AGENT.md

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+AGENTS.md

AGENTS.md

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+# Agent Instructions
+
+`AGENTS.md` is the canonical repo guidance for agents. Keep these instructions
+here and keep agent-specific entrypoints as symlinks to this file; do not edit
+the symlinks separately. `CLAUDE.md` points here for Claude Code. `AGENT.md`
+is a compatibility alias for singular agent-file readers; current Amp reads
+`AGENTS.md` directly and also recognizes `AGENT.md` only as a fallback.
+
+## Repo Shape
+
+- Version Guard is a Go service for infrastructure version drift detection.
+- Temporal workflows and activities are under `pkg/workflow`; keep workflow
+  code deterministic and put network, clock, and storage effects in activities.
+- The Helm chart lives in `charts/version-guard`; keep chart values, templates,
+  and chart metadata in sync when deployment behavior changes.
+- Resource definitions are config-driven in `pkg/config/defaults/resources.yaml`.
+  Prefer the transforms DSL in `TRANSFORMS.md` before adding custom code for
+  inventory reshaping.
+
+## Development Workflow
+
+- Read `CONTRIBUTING.md` before making changes that affect contribution flow,
+  release flow, CI expectations, or repository conventions.
+- Use the existing Makefile targets instead of one-off command variants:
+  `make build-all`, `make test`, `make test-ci`, `make lint`, `make fmt-all`,
+  and `make check`.
+- For chart changes, mirror the GitHub Actions workflow with
+  `ct lint --target-branch main --charts charts/version-guard` when chart-testing
+  is available.
+- Keep Go tests next to the package they cover. Prefer table-driven tests for
+  policy, parser, config, and transform behavior.
+- Run focused package tests while iterating, then the relevant Makefile target
+  before handing off.
+
+## Metrics And Docs
+
+- Do not claim custom application or business metrics unless the code implements
+  them. The supported metrics surface is the Temporal Go SDK Prometheus/OpenMetrics
+  endpoint exposed by the worker.
+- Keep documentation aligned with the Makefile, docker-compose setup, Temporal
+  workflow behavior, and Helm chart defaults.

CLAUDE.md

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+AGENTS.md