feat: add llms.txt standard support for AI agent discoverability (#784)

Cherry-picked website/, scripts/generate-llms-full.sh, and deploy-docs.yml
from joyshmitz's PR. Fixed workflow to trigger on main branch instead of
docs/docusaurus-site.

Features:
- Docusaurus documentation site with llms.txt support
- Environment-variable driven config (defaults to steveyegge org)
- Automated llms-full.txt generation from docs
- GitHub Pages deployment workflow

Co-authored-by: joyshmitz <joyshmitz@users.noreply.github.com>

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Executed-By: beads/crew/dave
Rig: beads
Role: crew

website/docs/core-concepts/index.md

@@ -0,0 +1,76 @@
+---
+id: index
+title: Core Concepts
+sidebar_position: 1
+---
+
+# Core Concepts
+
+Understanding the fundamental concepts behind beads.
+
+## Design Philosophy
+
+Beads was built with these principles:
+
+1. **Git as source of truth** - Issues sync via JSONL files, enabling collaboration across branches
+2. **AI-native workflows** - Hash-based IDs, JSON output, dependency-aware execution
+3. **Local-first operation** - SQLite database for fast queries, background sync
+4. **Declarative workflows** - Formulas define repeatable patterns
+
+## Key Components
+
+### Issues
+
+Work items with:
+- **ID** - Hash-based (e.g., `bd-a1b2`) or hierarchical (e.g., `bd-a1b2.1`)
+- **Type** - `bug`, `feature`, `task`, `epic`, `chore`
+- **Priority** - 0 (critical) to 4 (backlog)
+- **Status** - `open`, `in_progress`, `closed`
+- **Labels** - Flexible tagging
+- **Dependencies** - Blocking relationships
+
+### Dependencies
+
+Four types of relationships:
+
+| Type | Description | Affects Ready Queue |
+|------|-------------|---------------------|
+| `blocks` | Hard dependency (X blocks Y) | Yes |
+| `parent-child` | Epic/subtask relationship | No |
+| `discovered-from` | Track issues found during work | No |
+| `related` | Soft relationship | No |
+
+### Daemon
+
+Background process per workspace:
+- Auto-starts on first command
+- Handles auto-sync with 5s debounce
+- Socket at `.beads/bd.sock`
+- Manage with `bd daemons` commands
+
+### JSONL Sync
+
+The synchronization mechanism:
+
+```
+SQLite DB (.beads/beads.db)
+    ↕ auto-sync
+JSONL (.beads/issues.jsonl)
+    ↕ git
+Remote repository
+```
+
+### Formulas
+
+Declarative workflow templates:
+- Define steps with dependencies
+- Variable substitution
+- Gates for async coordination
+- Aspect-oriented transformations
+
+## Navigation
+
+- [Issues & Dependencies](/core-concepts/issues)
+- [Daemon Architecture](/core-concepts/daemon)
+- [JSONL Sync](/core-concepts/jsonl-sync)
+- [Hash-based IDs](/core-concepts/hash-ids)