docs: changelog entry for ecosystem miners

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: shahe-dev

CHANGELOG.md

@@ -4,6 +4,31 @@ All notable changes to engram are documented here. Format based on
 [Keep a Changelog](https://keepachangelog.com/en/1.1.0/); versioning follows
 [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+
+### Added
+
+- **`plugin-miner`** — indexes installed Claude Code plugins and their
+  provided agents as `concept` nodes with `metadata.subkind` of
+  `"plugin"` or `"agent"`. Plugin-provided skills are also indexed with
+  `subkind: "skill"`, scored against the project's detected stack, and
+  linked to their parent plugin via `provided_by` edges. Skills scored
+  EXTRACTED or INFERRED also get `relevant_to` edges to matching
+  project files.
+- **`config-miner`** — indexes configured hooks (`subkind: "hook"`) and
+  MCP servers (`subkind: "mcp_server"`) from `~/.claude/settings.json`
+  and `<project>/.claude/settings.local.json`. Always-on infrastructure
+  — confidence fixed at EXTRACTED 1.0, no `relevant_to` edges.
+- **`stack-detect`** utility (`src/graph/stack-detect.ts`) — pure
+  function that derives a set of lowercase language/framework tokens
+  from a snapshot of graph nodes. Single source of truth for stack
+  detection across miners.
+- **New `EdgeRelation` values**: `provided_by` and `relevant_to`.
+- Environment variable `ENGRAM_SKIP_ECOSYSTEM=1` disables both new
+  miners. Also gated behind the existing `options.withSkills` flag so
+  empty-project and stress tests stay isolated from the real
+  `~/.claude` tree.
+
 ## [0.5.0] — 2026-04-13 — "Context Spine"
 
 ### Added