Remove Makefile (use ./task directly) (#5167)

Drop the Makefile and route every remaining caller through \`./task\`
directly.

#5050 introduced \`./task\` and kept the Makefile as a thin shim.
eng-dev-ecosystem #1273 was the last external consumer; it now calls
\`go tool task\` directly, so the shim has no callers left and can go.

The shim was also broken: \`make integration\` was silently exiting 0
because \`integration/\` is a real directory (\`.DEFAULT\` doesn't apply
when the target name matches a file/directory). That's how
cli-isolated-nightly stopped producing \`output.json\` for ~5 days.

### Diff

- Delete \`Makefile\`.
- \`integration/README.md\`: \`make integration\` → \`./task
integration\`.
- \`experimental/ssh/README.md\`: \`make build snapshot-release\` →
\`./task build snapshot-release\`.
- \`tools/bench_parse.py\`: docstring example.

No CI changes needed — \`.github/workflows/\` already calls \`./task\`.

This pull request was AI-assisted by Isaac.

Author: shreyas-goenka

Makefile

@@ -19,7 +19,7 @@ databricks ssh connect --cluster=id
 
 ## Development
 ```shell
-make build snapshot-release
+./task build snapshot-release
 ./cli ssh connect --cluster=<id> --releases-dir=./dist --debug # or modify ssh config accordingly
 ```
 

experimental/ssh/README.md

@@ -33,5 +33,5 @@ go test ./integration/...
 Alternatively:
 
 ```bash
-make integration
+./task integration
 ```

integration/README.md

@@ -1,6 +1,6 @@
 #!/usr/bin/env python3
 """
-Parses output of benchmark runs (e.g. "make bench100") and prints a summary table.
+Parses output of benchmark runs (e.g. "./task bench-100") and prints a summary table.
 """
 
 import sys