feat(go-config): multi-format codecs, envc CLI, fixtures, ASRs

- Module github.com/eslider/go-config with env/yaml/json/ini packages
- internal: source, keymap, merge, structconv, bytesutil
- cmd/envc: convert, get, merge
- docs/asr ASR-0001..0008, README/CHANGELOG/AGENTS refresh
- golangci-lint v2 config; tests + fixtures

Co-authored-by: Cursor <cursoragent@cursor.com>

docs/asr/ASR-0001-module-rename-and-layout.md

@@ -0,0 +1,27 @@
+# ASR-0001: Module rename and multi-package layout
+
+## Context
+
+The original `github.com/eslider/go-env` module only decoded process environment variables. The product scope expanded to YAML, JSON, INI, URLs, multi-source merging, and a CLI. The old name and single-package layout no longer matched the capability surface.
+
+## Decision
+
+1. The canonical module path is **`github.com/eslider/go-config`**.
+2. Format-specific code lives in first-class subpackages: **`env/`**, **`yaml/`**, **`json/`**, **`ini/`**.
+3. Shared building blocks live under **`internal/{source,keymap,merge,structconv,bytesutil}`**.
+4. The CLI lives at **`cmd/envc/`** (one binary per inventar **ASR-0008** §2 — CLI inside the same module).
+5. The GitHub repository is named **`eSlider/go-config`** (renamed from `go-env`).
+
+## Consequences
+
+- Consumers must change their `import` paths and `go get` target.
+- CI, badges, and documentation reference `go-config` and `eslider/go-config`.
+
+## Status
+
+Accepted — 2026-05-02.
+
+## References
+
+- inventar ASR-0008 — Go library module conventions
+- ASR-0002 — API clean break