test(bash-lint): cover Python runtime bash generator in REQUIRED_STEP_DISPLAY_NAMES (#532)

Add python: true to runtime-coverage-agent.md so the lint exercises the
'Append Python prompt' bash step emitted by src/runtimes/python/extension.rs
via wrap_prompt_append(). Track the step in REQUIRED_STEP_DISPLAY_NAMES so
the coverage check catches regressions if the generator is renamed or removed.

No fixture previously included the Python runtime, leaving this bash step
completely outside the shellcheck quality gate.

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: github-actions[bot]

tests/bash_lint_tests.rs

@@ -103,6 +103,7 @@ const REQUIRED_STEP_DISPLAY_NAMES: &[&str] = &[
     "Ensure nuget.config exists",             // src/runtimes/dotnet/mod.rs
     "Restore previous agent memory",          // src/tools/cache_memory/extension.rs
     "Initialize empty agent memory (clearMemory=true)",
+    "Append Python prompt",                   // src/runtimes/python/extension.rs
     "Generate GITHUB_PATH file",              // src/compile/common.rs (AWF path step)
     "Evaluate pipeline filters",              // src/compile/extensions/trigger_filters.rs + src/compile/filter_ir.rs
     "Evaluate PR filters",                    // src/compile/filter_ir.rs (GateContext::PullRequest)

tests/fixtures/runtime-coverage-agent.md

@@ -5,6 +5,7 @@ on:
   schedule: daily
 runtimes:
   lean: true
+  python: true
   node:
     version: "22.x"
     feed-url: "https://pkgs.dev.azure.com/example/example/_packaging/example/npm/registry/"
@@ -19,4 +20,5 @@ tools:
 
 This agent enables every runtime that produces a code-generated bash step,
 plus the `cache-memory` tool. Its sole job is to compile cleanly so the
-bash-step lint can analyse those generated bodies.
+bash-step lint can analyse those generated bodies. Python is included to
+exercise the `Append Python prompt` step from `src/runtimes/python/extension.rs`.