Replace legacy scripts with separated ots/node hooks

- Remove deprecated scripts/ directory (6 files)
- Add hooks/post-commit-ots (ots CLI version)
- Add hooks/pre-commit-ots (ots CLI backfill)
- Add hooks/post-commit-node (Node.js version, local proofs only)
- Add hooks/pre-commit-node (Node.js backfill, no upgrade)
- Update hooks/install.sh to auto-detect and install matching hooks
- Update documentation (SKILL.md, README.md, AGENTS.md)
- Add node_modules/ to .gitignore for Node.js mode

Breaking change: Scripts removed, use new hooks/ directory.

AGENTS.md

@@ -9,15 +9,13 @@ Use this skill when the user wants to:
 - Create cryptographic proof of commit history
 - Anchor commits to Bitcoin blockchain via OpenTimestamp
 
-## Installation (Recommended)
-
-**Self-contained hooks** - No external dependencies:
+## Installation (Auto-Detect)
 
 ```bash
-# 1. Install prerequisites
+# 1. Install prerequisites (ots CLI recommended)
 pipx install opentimestamps-client
 
-# 2. Install hooks (single command)
+# 2. Install hooks (auto-detects available tools)
 ./hooks/install.sh .
 
 # 3. Commit proofs to repository
@@ -25,31 +23,48 @@ git add .ots/ .gitignore
 git commit -m "Add OpenTimestamp proofs for commit history"
 ```
 
-## Installation (Manual)
+## Installation Modes
 
-Copy hook files directly:
+The installer auto-detects and installs matching hooks:
 
+| Detected | Hooks Installed | Attestation |
+|----------|----------------|-------------|
+| `ots` CLI | `post-commit-ots`, `pre-commit-ots` | Full Bitcoin |
+| `@opentimestamps/ots` (node) | `post-commit-node`, `pre-commit-node` | Local only |
+
+**Recommendation:** Always prefer ots CLI for production use.
+
+## Manual Installation
+
+### ots CLI Mode
 ```bash
-cp hooks/post-commit .git/hooks/
-cp hooks/pre-commit .git/hooks/
-chmod +x .git/hooks/post-commit .git/hooks/pre-commit
+cp hooks/post-commit-ots .git/hooks/
+cp hooks/pre-commit-ots .git/hooks/
+chmod +x .git/hooks/*
 ```
 
-**.gitignore**:
-```
-.ots/.attestation-cache
+### Node.js Mode
+```bash
+cp hooks/post-commit-node .git/hooks/
+cp hooks/pre-commit-node .git/hooks/
+chmod +x .git/hooks/*
+npm install @opentimestamps/ots  # If not already installed
 ```
 
 ## Key Files
 
 | File | Purpose | Version? |
 |------|---------|----------|
-| `generate-proof.sh` | Creates proof for commit | Yes |
-| `backfill-proofs.sh` | Upgrades all historical proofs | Yes |
-| `install-ots-hook.sh` | Installs both hooks | Yes |
-| `.ots/*.ots` | Binary proofs | Yes |
+| `hooks/post-commit-ots` | Post-commit hook (ots CLI) | Yes |
+| `hooks/pre-commit-ots` | Backfill hook (ots CLI) | Yes |
+| `hooks/post-commit-node` | Post-commit hook (Node.js) | Yes |
+| `hooks/pre-commit-node` | Backfill hook (Node.js) | Yes |
+| `hooks/install.sh` | Auto-detect installer | Yes |
+| `.ots/*.ots` | Individual proofs | Yes |
+| `.ots/proof.ots` | Latest proof reference | Yes |
 | `.ots/commit-chain.txt` | Commit chain | Yes |
 | `.ots/.attestation-cache` | Local cache | No |
+| `node_modules/` | Node dependencies (if used) | No |
 
 ## Verification
 
@@ -67,4 +82,5 @@ ots verify .ots/<commit-hash>.ots
 - Proofs take ~10 min to become Bitcoin-attested
 - Cache avoids redundant calendar calls (1-hour validity)
 - Pre-commit backfill adds ~10-15s to commit time
-- Safe to commit `.ots/` directory (binary proofs are small: ~500B each)
+- Node.js version creates local proofs only (no calendar submission)
+- Safe to commit `.ots/` directory (binary proofs are ~500-900B each)