Auto-generate distro yamls + docs (#468)

# What does this PR do?

Automatically generates
- build.yaml
- run.yaml
- run-with-safety.yaml
- parts of markdown docs

for the distributions.

## Test Plan

At this point, this only updates the YAMLs and the docs. Some testing
(especially with ollama and vllm) has been performed but needs to be
much more tested.

llama_stack/cli/stack/run.py

@@ -39,6 +39,13 @@ class StackRun(Subcommand):
             help="Disable IPv6 support",
             default=False,
         )
+        self.parser.add_argument(
+            "--env",
+            action="append",
+            help="Environment variables to pass to the server in KEY=VALUE format. Can be specified multiple times.",
+            default=[],
+            metavar="KEY=VALUE",
+        )
 
     def _run_stack_run_cmd(self, args: argparse.Namespace) -> None:
         from pathlib import Path
@@ -108,4 +115,16 @@ class StackRun(Subcommand):
         if args.disable_ipv6:
             run_args.append("--disable-ipv6")
 
+        for env_var in args.env:
+            if "=" not in env_var:
+                self.parser.error(
+                    f"Environment variable '{env_var}' must be in KEY=VALUE format"
+                )
+                return
+            key, value = env_var.split("=", 1)  # split on first = only
+            if not key:
+                self.parser.error(f"Environment variable '{env_var}' has empty key")
+                return
+            run_args.extend(["--env", f"{key}={value}"])
+
         run_with_pty(run_args)