docs(test): move snapshots.toml comment to per-[[e2e]] level (#347)

## Summary

- Drops the file-level `comment` field from `snapshots.toml` in the e2e
harness; a `comment` now lives on each `[[e2e]]` entry and renders under
that case's H1 heading.
- Migrates every existing top-level comment into per-case comments, each
written to describe what that individual case verifies (cache behaviors,
stdio modes, selector flows, etc.).

## Test plan

- [ ] `cargo test -p vite_task_bin --test e2e_snapshots` passes (148/148
locally)
- [ ] Spot-check a few regenerated `.md` snapshots to confirm the new
comments read sensibly under each H1

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: branchseer

crates/vite_task_bin/tests/e2e_snapshots/fixtures/associate_existing_cache/snapshots.toml

@@ -1,9 +1,8 @@
+[[e2e]]
+name = "associate_existing_cache"
 comment = """
 Tests that tasks with identical commands share cache
 """
-
-[[e2e]]
-name = "associate_existing_cache"
 steps = [
   { argv = [
     "vt",

crates/vite_task_bin/tests/e2e_snapshots/fixtures/builtin_different_cwd/snapshots.toml

@@ -1,9 +1,8 @@
+[[e2e]]
+name = "builtin_different_cwd"
 comment = """
 Tests that synthetic tasks have separate cache per cwd
 """
-
-[[e2e]]
-name = "builtin_different_cwd"
 steps = [
   { argv = [
     "vt",

crates/vite_task_bin/tests/e2e_snapshots/fixtures/cache_disabled/snapshots.toml

@@ -1,9 +1,8 @@
-comment = """
-Tests that cache: false in task config disables caching
-"""
-
 [[e2e]]
 name = "task_with_cache_disabled"
+comment = """
+A task configured with `cache: false` should re-run on every invocation instead of being cached.
+"""
 steps = [
   { argv = [
     "vt",
@@ -19,6 +18,9 @@ steps = [
 
 [[e2e]]
 name = "task_with_cache_enabled"
+comment = """
+A task with caching enabled should produce a cache hit on the second run.
+"""
 steps = [
   { argv = [
     "vt",

crates/vite_task_bin/tests/e2e_snapshots/fixtures/cache_disabled/snapshots/task_with_cache_disabled.md

@@ -1,6 +1,6 @@
 # task_with_cache_disabled
 
-Tests that cache: false in task config disables caching
+A task configured with `cache: false` should re-run on every invocation instead of being cached.
 
 ## `vt run no-cache-task`
 

crates/vite_task_bin/tests/e2e_snapshots/fixtures/cache_disabled/snapshots/task_with_cache_enabled.md

@@ -1,6 +1,6 @@
 # task_with_cache_enabled
 
-Tests that cache: false in task config disables caching
+A task with caching enabled should produce a cache hit on the second run.
 
 ## `vt run cached-task`
 

crates/vite_task_bin/tests/e2e_snapshots/fixtures/cache_miss_command_change/snapshots.toml

@@ -1,9 +1,8 @@
+[[e2e]]
+name = "cache_miss_command_change"
 comment = """
 Tests cache behavior when command changes partially
 """
-
-[[e2e]]
-name = "cache_miss_command_change"
 steps = [
   { argv = [
     "vt",

crates/vite_task_bin/tests/e2e_snapshots/fixtures/cache_miss_reasons/snapshots.toml

@@ -1,9 +1,8 @@
-comment = """
-Test all cache miss reason variants
-"""
-
 [[e2e]]
 name = "env_value_changed"
+comment = """
+Changing the value of a tracked env var between runs should invalidate the cache.
+"""
 steps = [
   { argv = [
     "vt",
@@ -29,6 +28,9 @@ steps = [
 
 [[e2e]]
 name = "env_added"
+comment = """
+Setting a tracked env var that was previously unset should invalidate the cache.
+"""
 steps = [
   { argv = [
     "vt",
@@ -49,6 +51,9 @@ steps = [
 
 [[e2e]]
 name = "env_removed"
+comment = """
+Unsetting a tracked env var that was previously set should invalidate the cache.
+"""
 steps = [
   { argv = [
     "vt",
@@ -69,6 +74,9 @@ steps = [
 
 [[e2e]]
 name = "untracked_env_added"
+comment = """
+Adding an `untrackedEnv` entry to the task config should invalidate the cache.
+"""
 steps = [
   { argv = [
     "vt",
@@ -91,6 +99,9 @@ steps = [
 
 [[e2e]]
 name = "untracked_env_removed"
+comment = """
+Removing an existing `untrackedEnv` entry from the task config should invalidate the cache.
+"""
 steps = [
   { argv = [
     "vtt",
@@ -120,6 +131,9 @@ steps = [
 
 [[e2e]]
 name = "cwd_changed"
+comment = """
+Changing the task's `cwd` should invalidate the cache, even if the input file exists at the new location.
+"""
 steps = [
   { argv = [
     "vt",
@@ -154,6 +168,9 @@ steps = [
 
 [[e2e]]
 name = "inferred_input_changes"
+comment = """
+Modifying, removing, and re-adding an input file (tracked via fspy inference) should each invalidate the cache.
+"""
 steps = [
   { argv = [
     "vt",
@@ -197,6 +214,9 @@ steps = [
 
 [[e2e]]
 name = "input_config_changed"
+comment = """
+Changing the task's `input` configuration should invalidate the cache even when the underlying files are unchanged.
+"""
 steps = [
   { argv = [
     "vt",
@@ -219,6 +239,9 @@ steps = [
 
 [[e2e]]
 name = "glob_input_changes"
+comment = """
+Modifying, adding, or removing files matched by a glob `input` pattern should each invalidate the cache.
+"""
 steps = [
   { argv = [
     "vt",

crates/vite_task_bin/tests/e2e_snapshots/fixtures/cache_miss_reasons/snapshots/cwd_changed.md

@@ -1,6 +1,6 @@
 # cwd_changed
 
-Test all cache miss reason variants
+Changing the task's `cwd` should invalidate the cache, even if the input file exists at the new location.
 
 ## `vt run test`
 

crates/vite_task_bin/tests/e2e_snapshots/fixtures/cache_miss_reasons/snapshots/env_added.md

@@ -1,6 +1,6 @@
 # env_added
 
-Test all cache miss reason variants
+Setting a tracked env var that was previously unset should invalidate the cache.
 
 ## `vt run test`
 

crates/vite_task_bin/tests/e2e_snapshots/fixtures/cache_miss_reasons/snapshots/env_removed.md

@@ -1,6 +1,6 @@
 # env_removed
 
-Test all cache miss reason variants
+Unsetting a tracked env var that was previously set should invalidate the cache.
 
 ## `MY_ENV=1 vt run test`