[groupsky]

Refs #92

Interactive zsh does not treat # as a comment unless interactivecomments is on (off by default). So a pasted cmd # note line passes # and the note to cmd. This PR puts each such note on its own line above the command, and adds a test that finds new ones.

Progress

• No shell block in README.md, AGENTS.md or docs/ has a command line that ends in a # comment (19 lines moved: README, AGENTS, setup, both manual tests).
• A short check finds none: docs_test.go, TestDocsShellLinesHaveNoTrailingComment. It runs in the normal go test ./... in CI. TestTrailingShellComments checks the finder itself (quotes, $#, URLs with #, TOML blocks, indented blocks).

Choices

• A Go test, not a CI script: it runs with go test ./... already, needs no new tool, and runs on every developer's machine too.
• It reads every Markdown file at the root and in docs/ (not only README, AGENTS and docs/, so that DESIGN.md is covered too), and blocks marked sh, bash, shell, zsh or console. All shell blocks in the docs are marked sh. TOML and other blocks are not checked (their comments are config, not shell).
• A note on its own line still makes zsh print command not found: # (when interactivecomments is off). That is harmless: no command gets extra words. The issue asks for this form.

Review

• Review subagent: no problems.
• security-reviewer: no security findings. Its low notes (cover all Markdown files; say the harmless zsh error in the test comment) are fixed in 2nd commit. Not fixed: ~~~ fences and quotes over many lines; the docs use neither today.