feat: add CLI aliases, flatten trade commands, and introduce --doc

- Add `coin` entry-point alias alongside `coinhunter`
- Add short aliases for all commands (e.g., a/acc, m, opp/o, b, s)
- Flatten `buy` and `sell` to top-level commands; remove `trade` parent
- Add `--doc` flag to print output schema and field descriptions per command
- Update README and tests
- Bump version to 2.1.0

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

README.md

@@ -28,6 +28,12 @@ pipx install coinhunter
 coinhunter --help
 ```
 
+You can also use the shorter `coin` alias:
+
+```bash
+coin --help
+```
+
 Check the installed version:
 
 ```bash
@@ -68,28 +74,45 @@ Override the default home directory with `COINHUNTER_HOME`.
 
 By default, CoinHunter prints human-friendly TUI tables. Add `--agent` to any command to get JSON output (or compact pipe-delimited tables for large datasets).
 
+Add `--doc` to any command to see its output schema and field descriptions (great for AI agents):
+
 ```bash
-# Account
+coin buy --doc
+coin market klines --doc
+```
+
+### Examples
+
+```bash
+# Account (aliases: a, acc)
 coinhunter account overview
 coinhunter account overview --agent
-coinhunter account balances
-coinhunter account positions
+coin a ov
+coin acc bal
+coin a pos
 
-# Market
+# Market (aliases: m)
 coinhunter market tickers BTCUSDT ETH/USDT sol-usdt
 coinhunter market klines BTCUSDT ETHUSDT --interval 1h --limit 50
+coin m tk BTCUSDT ETHUSDT
+coin m k BTCUSDT -i 1h -l 50
 
-# Trade
-coinhunter trade buy BTCUSDT --quote 100 --dry-run
-coinhunter trade sell BTCUSDT --qty 0.01 --type limit --price 90000
+# Trade (buy / sell are now top-level commands)
+coinhunter buy BTCUSDT --quote 100 --dry-run
+coinhunter sell BTCUSDT --qty 0.01 --type limit --price 90000
+coin b BTCUSDT -Q 100 -d
+coin s BTCUSDT -q 0.01 -t limit -p 90000
 
-# Opportunities
+# Opportunities (aliases: opp, o)
 coinhunter opportunity portfolio
 coinhunter opportunity scan
 coinhunter opportunity scan --symbols BTCUSDT ETHUSDT SOLUSDT
+coin opp pf
+coin o scan -s BTCUSDT ETHUSDT
 
 # Self-upgrade
 coinhunter upgrade
+coin upgrade
 
 # Shell completion (manual)
 coinhunter completion zsh  > ~/.zsh/completions/_coinhunter