chore: track Nx 22 AI tooling artefacts injected by generators

Nx 22 generators inject AI agent tooling into the repo via marked
sections and side files. Rather than re-deleting them after every
generator run, track the workspace-level ones and document why.

- CLAUDE.md gains a 'General Guidelines for working with Nx' section
  between Nx-managed markers; future Nx versions will update this
  section automatically without touching our project rules above.
  Pre-existing prettier-formatted blank lines added before code blocks
  are kept.
- .claude/settings.json (228 bytes) enables the nx-claude-plugins
  marketplace from nrwl/nx-ai-agents-config; tracked for contributor
  consistency. The personal .claude/settings.local.json stays
  gitignored.
- .github/ is the Nx AI skills/prompts/agents catalog. Kept despite
  being GitHub-named; it does not conflict with our Gitea workflows
  which will live under .gitea/workflows/ (per ADR-0015).
- .gitignore picks up Nx-managed transient dirs (.nx/polygraph,
  .claude/worktrees) and a trailing newline fix.

AGENTS.md is removed: it duplicated only the Nx auto-injected guidance
that CLAUDE.md already carries (CLAUDE.md is the strictly broader file
- project rules + Nx section). One source of truth for AI-agent
guidance.

.github/skills/link-workspace-packages/SKILL.md

@@ -0,0 +1,127 @@
+---
+name: link-workspace-packages
+description: 'Link workspace packages in monorepos (npm, yarn, pnpm, bun). USE WHEN: (1) you just created or generated new packages and need to wire up their dependencies, (2) user imports from a sibling package and needs to add it as a dependency, (3) you get resolution errors for workspace packages (@org/*) like "cannot find module", "failed to resolve import", "TS2307", or "cannot resolve". DO NOT patch around with tsconfig paths or manual package.json edits - use the package manager''s workspace commands to fix actual linking.'
+---
+
+# Link Workspace Packages
+
+Add dependencies between packages in a monorepo. All package managers support workspaces but with different syntax.
+
+## Detect Package Manager
+
+Check whether there's a `packageManager` field in the root-level `package.json`.
+
+Alternatively check lockfile in repo root:
+
+- `pnpm-lock.yaml` → pnpm
+- `yarn.lock` → yarn
+- `bun.lock` / `bun.lockb` → bun
+- `package-lock.json` → npm
+
+## Workflow
+
+1. Identify consumer package (the one importing)
+2. Identify provider package(s) (being imported)
+3. Add dependency using package manager's workspace syntax
+4. Verify symlinks created in consumer's `node_modules/`
+
+---
+
+## pnpm
+
+Uses `workspace:` protocol - symlinks only created when explicitly declared.
+
+```bash
+# From consumer directory
+pnpm add @org/ui --workspace
+
+# Or with --filter from anywhere
+pnpm add @org/ui --filter @org/app --workspace
+```
+
+Result in `package.json`:
+
+```json
+{ "dependencies": { "@org/ui": "workspace:*" } }
+```
+
+---
+
+## yarn (v2+/berry)
+
+Also uses `workspace:` protocol.
+
+```bash
+yarn workspace @org/app add @org/ui
+```
+
+Result in `package.json`:
+
+```json
+{ "dependencies": { "@org/ui": "workspace:^" } }
+```
+
+---
+
+## npm
+
+No `workspace:` protocol. npm auto-symlinks workspace packages.
+
+```bash
+npm install @org/ui --workspace @org/app
+```
+
+Result in `package.json`:
+
+```json
+{ "dependencies": { "@org/ui": "*" } }
+```
+
+npm resolves to local workspace automatically during install.
+
+---
+
+## bun
+
+Supports `workspace:` protocol (pnpm-compatible).
+
+```bash
+cd packages/app && bun add @org/ui
+```
+
+Result in `package.json`:
+
+```json
+{ "dependencies": { "@org/ui": "workspace:*" } }
+```
+
+---
+
+## Examples
+
+**Example 1: pnpm - link ui lib to app**
+
+```bash
+pnpm add @org/ui --filter @org/app --workspace
+```
+
+**Example 2: npm - link multiple packages**
+
+```bash
+npm install @org/data-access @org/ui --workspace @org/dashboard
+```
+
+**Example 3: Debug "Cannot find module"**
+
+1. Check if dependency is declared in consumer's `package.json`
+2. If not, add it using appropriate command above
+3. Run install (`pnpm install`, `npm install`, etc.)
+
+## Notes
+
+- Symlinks appear in `<consumer>/node_modules/@org/<package>`
+- **Hoisting differs by manager:**
+  - npm/bun: hoist shared deps to root `node_modules`
+  - pnpm: no hoisting (strict isolation, prevents phantom deps)
+  - yarn berry: uses Plug'n'Play by default (no `node_modules`)
+- Root `package.json` should have `"private": true` to prevent accidental publish