feat(skills): add quill-code skill

Local dev loop for the @posthog/quill design system: edit quill in the sibling mono, build the whole quill workspace, pack a content-hashed tarball into .local-quill, repoint the pnpm override, and reinstall — so quill changes can be tested in this app before publishing.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: adamleithp

.claude/skills/quill-code/SKILL.md

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+---
+name: quill-code
+description: Edit the @posthog/quill design system locally and consume the change in this repo (posthog-code) before it is published to npm. Use when changing quill components/primitives/tokens, when a quill change must be tested inside the Code app, or when the user mentions quill, the design system, the .local-quill tarball, or the @posthog/quill pnpm override.
+---
+
+# quill-code
+
+`@posthog/quill` is **not** in this repo. It is a published catalog dependency whose
+source lives in the main PostHog monorepo at `../posthog/packages/quill`. To test an
+unpublished quill change inside this repo (posthog-code), you build quill, pack it to a
+tarball, and point a pnpm `overrides` entry at that tarball. This is a **temporary
+local-dev** state — revert before merging (see below).
+
+## Quill layout (where to edit)
+
+`../posthog/packages/quill` is the **workspace** (`@posthog/quill-workspace`). It
+contains sub-packages, each a layer of the design system:
+
+- `packages/primitives/src` — base components (Card, Badge, Button, Progress, …)
+- `packages/components/src` — composed components (DataTable, DateTimePicker, Metric)
+- `packages/blocks/src` — **product-level blocks** (e.g. `ExperimentCard`). Add the
+  file here and export it from `packages/blocks/src/index.ts`.
+- `packages/quill/src` — the **aggregate** that re-exports all layers as `@posthog/quill`.
+
+A new export in any sub-package flows to `@posthog/quill` automatically on build.
+
+## The loop (every quill change)
+
+1. Edit/add the component in the right sub-package (above) and export it from that
+   package's `src/index.ts`.
+2. Re-sync into this repo:
+
+   ```bash
+   .claude/skills/quill-code/scripts/sync-quill.sh
+   ```
+
+   This builds the **whole quill workspace** (recursive `pnpm build` at the workspace
+   root — it rebuilds the sub-packages BEFORE the aggregate bundles them), packs it
+   into `.local-quill/` as a content-hashed `posthog-quill-local-<hash>.tgz`, rewrites
+   the override line in `pnpm-workspace.yaml`, deletes stale tarballs, and runs
+   `pnpm install`.
+
+   > Building only the aggregate (`packages/quill/packages/quill`) re-bundles the
+   > sub-packages' **stale** `dist/`, so edits to primitives/components/blocks are
+   > silently dropped. Always build at the workspace root — the script does this.
+3. Verify in the Code app (`pnpm dev`, or the `test-electron-app` skill). Repeat from 1.
+
+After every quill edit you **must** re-run the sync — the app consumes the tarball, not
+the quill source, so unsynced edits are invisible here.
+
+If quill lives elsewhere, set `QUILL_DIR=/abs/path/to/posthog/packages/quill/packages/quill`.
+
+## Why a tarball, not `link:`
+
+`link:` symlinks into the mono's `node_modules` and drags in its **React 18** types,
+colliding with this repo's **React 19** (dual-React → broken typecheck +
+invalid-hook-call at runtime). The tarball is copied into this repo's store and deduped
+against React 19. The filename is **content-hashed** because pnpm pins a tarball by
+integrity, so a stable filename gets cached stale across re-syncs.
+
+## The override (what the script rewrites)
+
+In `pnpm-workspace.yaml`, under `overrides:`:
+
+```yaml
+'@posthog/quill': file:./.local-quill/posthog-quill-local-<hash>.tgz
+```
+
+There is also a permanent pin you should leave alone:
+
+```yaml
+'@posthog/quill>@base-ui/react': ^1.3.0   # quill ships a broken catalog: dep; do not remove
+```
+
+## Reverting (before merge)
+
+The override is local-dev only. Once the quill change is published to npm:
+
+1. Bump the catalog version in `pnpm-workspace.yaml` (`'@posthog/quill': 0.3.0-beta.x`)
+   to the published version.
+2. Restore the override line to point back at the catalog, or remove the `file:` override.
+3. `pnpm install`.
+
+Do not commit a `file:./.local-quill/...` override or the `.local-quill/` tarballs.

.claude/skills/quill-code/scripts/sync-quill.sh

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+#!/usr/bin/env bash
+# Build local @posthog/quill, pack it to a content-hashed tarball, point the
+# pnpm override at it, and reinstall. See SKILL.md for the why.
+set -euo pipefail
+
+# code repo root = dir containing pnpm-workspace.yaml, walking up from this script
+CODE_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")" && while [ ! -f pnpm-workspace.yaml ] && [ "$PWD" != / ]; do cd ..; done && pwd)"
+[ -f "$CODE_ROOT/pnpm-workspace.yaml" ] || { echo "could not find pnpm-workspace.yaml above $0" >&2; exit 1; }
+
+QUILL_DIR="${QUILL_DIR:-$CODE_ROOT/../posthog/packages/quill/packages/quill}"
+[ -d "$QUILL_DIR" ] || { echo "quill source not found: $QUILL_DIR (set QUILL_DIR=...)" >&2; exit 1; }
+
+# The quill workspace root (@posthog/quill-workspace) is two levels up from the
+# aggregate package. We MUST build there: its `pnpm build` runs the recursive
+# `pnpm -r --filter '@posthog/quill-*' --filter '@posthog/quill' build`, which
+# rebuilds the sub-packages (primitives, components, blocks, ...) BEFORE the
+# aggregate bundles them. Building inside QUILL_DIR alone only re-bundles the
+# sub-packages' STALE dist, so edits to blocks/primitives/etc. are silently lost.
+QUILL_WS="${QUILL_WS:-$(cd "$QUILL_DIR/../.." && pwd)}"
+
+DEST="$CODE_ROOT/.local-quill"
+WS="$CODE_ROOT/pnpm-workspace.yaml"
+
+echo "==> building quill workspace in $QUILL_WS"
+( cd "$QUILL_WS" && pnpm build )
+
+echo "==> packing tarball -> $DEST"
+mkdir -p "$DEST"
+( cd "$QUILL_DIR" && npm pack --pack-destination "$DEST" >/dev/null )
+
+RAW="$(ls -t "$DEST"/posthog-quill-*.tgz | grep -v -- '-local-' | head -1)"
+[ -n "$RAW" ] || { echo "npm pack produced no posthog-quill-*.tgz" >&2; exit 1; }
+
+HASH="$(md5 -q "$RAW" | cut -c1-8)"
+HASHED="posthog-quill-local-$HASH.tgz"
+cp "$RAW" "$DEST/$HASHED"
+rm -f "$RAW"
+# drop stale local tarballs so the pnpm store can't resolve an old integrity
+find "$DEST" -name 'posthog-quill-local-*.tgz' ! -name "$HASHED" -delete
+
+echo "==> pointing override at .local-quill/$HASHED"
+# single override line: '@posthog/quill': file:./.local-quill/...
+sed -i '' -E "s#('@posthog/quill': file:\./\.local-quill/)[^']*#\1$HASHED#" "$WS"
+grep -q "$HASHED" "$WS" || { echo "failed to rewrite override line in $WS" >&2; exit 1; }
+
+echo "==> pnpm install"
+( cd "$CODE_ROOT" && pnpm install )
+
+echo "==> done. @posthog/quill now resolves to .local-quill/$HASHED"