feat(a): improve encryption script with better error handling

- Add dependency check for age and curl with install instructions
- Add --delete flag to remove originals after encryption
- Add -f/--force flag to control overwrite behavior
- Skip already-encrypted .age files during encryption
- Include hidden files (dotglob) when encrypting directories
- Handle empty directories gracefully with nullglob
- Allow flags in any position (proper option parsing)
- Add set -euo pipefail for better error handling
- Update documentation with all features and examples
- Bump version to 1.1.0

local/bin/a.md

@@ -2,28 +2,76 @@
 
 Encrypt or decrypt files and directories using `age` and your GitHub SSH keys.
 
+## Requirements
+
+- [age](https://github.com/FiloSottile/age) - encryption tool
+- curl - for fetching SSH keys
+
+Install age:
+
+```bash
+brew install age     # macOS
+apt install age      # Debian/Ubuntu
+dnf install age      # Fedora
+```
+
 ## Usage
 
 ```bash
-a encrypt <file|dir>
-a decrypt <file.age|dir>
+a [options] <command> <file|directory>
 ```
 
+Commands:
+
+- `e`, `enc`, `encrypt` - encrypt files
+- `d`, `dec`, `decrypt` - decrypt files
+- `help`, `--help`, `-h` - show help
+- `version`, `--version` - show version
+
 Options:
 
-- `-v`, `--verbose` – show log output
+- `-v`, `--verbose` - show log output
+- `--delete` - delete original files after successful operation
+- `-f`, `--force` - overwrite existing output files
 
 Environment variables:
 
-- `AGE_KEYSFILE` – location of the keys file
-- `AGE_KEYSSOURCE` – URL to fetch keys if missing
-- `AGE_LOGFILE` – log file path
+- `AGE_KEYSFILE` - location of the keys file (default: `~/.ssh/keys.txt`)
+- `AGE_KEYSSOURCE` - URL to fetch keys if missing (default: GitHub keys)
+- `AGE_LOGFILE` - log file path (default: `~/.cache/a.log`)
 
-## Example
+## Examples
 
 ```bash
+# Encrypt a file
 a encrypt secret.txt
+
+# Encrypt with short command
+a e secret.txt
+
+# Decrypt a file
 a decrypt secret.txt.age
+a d secret.txt.age
+
+# Encrypt a directory (includes hidden files)
+a e /path/to/secrets/
+
+# Encrypt and delete originals
+a --delete e secret.txt
+
+# Force overwrite existing .age file
+a -f e secret.txt
+
+# Verbose output
+a -v e secret.txt
 ```
 
+## Behavior
+
+- Encrypting a directory processes all files recursively, including hidden files
+- Already encrypted files (`.age`) are skipped during encryption
+- Only `.age` files are processed during directory decryption
+- Original files are preserved by default (use `--delete` to remove them)
+- Output files are not overwritten by default (use `--force` to overwrite)
+
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