chore: add changeset for app concept and query pagination

Author: ericallam

.changeset/app-concept-and-pagination.md

@@ -0,0 +1,29 @@
+---
+"agentcrumbs": minor
+---
+
+Add app concept for project-level crumb isolation and cursor-based query pagination.
+
+**App isolation:**
+- Every crumb is stamped with an `app` name, auto-detected from the nearest `package.json`
+- Crumbs stored per-app at `~/.agentcrumbs/<app>/crumbs.jsonl`
+- Collector routes incoming crumbs to per-app stores
+- All CLI commands scope to the current app by default
+- Override with `--app <name>`, `--all-apps`, `AGENTCRUMBS_APP` env var, or `app` field in JSON config
+
+**Query pagination:**
+- New `--cursor` flag for forward pagination with short 8-char cursor IDs
+- New `--after` and `--before` flags for absolute ISO timestamp windows
+- Default limit reduced from 100 to 50 per page
+- Results returned oldest-first with `Next: --cursor <id>` in output when more pages exist
+
+**New files:**
+- `src/cli/app-store.ts` — shared helper for app context resolution across CLI commands
+- `src/cli/cursor.ts` — cursor storage with 1-hour TTL
+
+**Breaking changes:**
+- `Crumb` type now has a required `app: string` field
+- `AgentCrumbsConfig` type now has an optional `app?: string` field
+- `CollectorServer` no longer exposes `getStore()` (routes to per-app stores internally)
+- Storage location changed from `~/.agentcrumbs/crumbs.jsonl` to `~/.agentcrumbs/<app>/crumbs.jsonl`
+- Legacy flat-file crumbs (without `app` field) are still readable as app `"unknown"`