docs: add README and CLAUDE.md

README with open source install instructions (project-level and user-level),
copy-paste CLAUDE.md snippet for users, command reference, and architecture.
CLAUDE.md with dev workflow for contributors.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -0,0 +1,20 @@
+# gstack-browse development
+
+## Commands
+
+```bash
+bun install          # install dependencies
+bun test             # run integration tests (40 tests with fixture server)
+bun run dev <cmd>    # run CLI in dev mode, e.g. bun run dev goto https://example.com
+bun run build        # compile binary to dist/browse
+```
+
+## Deploying to the active skill
+
+The active skill lives at `~/.claude/skills/gstack-browse/`. After making changes:
+
+1. Push your branch
+2. Pull in the skill directory: `cd ~/.claude/skills/gstack-browse && git pull`
+3. Rebuild: `cd ~/.claude/skills/gstack-browse && bun run build`
+
+Or copy the binary directly: `cp dist/browse ~/.claude/skills/gstack-browse/dist/browse`