chore: clean up after object dependsOn reverts

The mechanical reverts of #467 and #469 could not account for changes that
landed on main afterwards:

- #477 renamed plan task-graph snapshots from `.jsonc` to `.md`, so reverting
  the `depends_on_package_dependencies` fixture left `snapshots/task_graph.md`
  behind as an orphan with no package. The plan snapshot harness runs every
  fixture directory through workspace discovery, so this stale directory would
  fail the suite — remove it.
- `vec1` was used only by the reverted object-form `dependsOn` config, so it is
  now an unused dependency of `vite_task_graph` that `cargo shear` rejects —
  drop it.
- Reverting #467's `task-query.md` edits would reintroduce the internal
  `vite-task.json` name into published docs; keep the public `vite.config.*`
  spelling that main already uses.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QowxsN8vDKKbQdaSMdxL67

Author: claude

Cargo.lock

@@ -7,7 +7,7 @@ How `vp run` decides which tasks to run and in what order.
 When `vp` starts, it builds two data structures from the workspace:
 
 1. **Package graph** — which packages depend on which. Built from `package.json` dependency fields.
-2. **Task graph** — which tasks exist and their explicit `dependsOn` relationships. Built from `vite-task.json` and `package.json` scripts.
+2. **Task graph** — which tasks exist and their explicit `dependsOn` relationships. Built from `vite.config.*` and `package.json` scripts.
 
 Both are built once and reused for every query, including nested `vp run` calls inside task scripts.
 
@@ -16,7 +16,7 @@ Both are built once and reused for every query, including nested `vp run` calls
 The task graph contains a node for every task in every package, and edges only for explicit `dependsOn` declarations:
 
 ```jsonc
-// packages/app/vite-task.json
+// packages/app/vite.config.*
 {
   "tasks": {
     "build": {
@@ -174,7 +174,7 @@ So we clone the `DiGraphMap` once and mutate the clone. We iterate the original
 After mapping the package subgraph to tasks, we follow explicit `dependsOn` edges from the task graph. This can pull in tasks from packages outside the selected set.
 
 ```jsonc
-// packages/app/vite-task.json
+// packages/app/vite.config.*
 {
   "tasks": {
     "build": {

crates/vite_task/docs/task-query.md

@@ -18,7 +18,6 @@ serde = { workspace = true, features = ["derive"] }
 serde_json = { workspace = true }
 thiserror = { workspace = true }
 tracing = { workspace = true }
-vec1 = { workspace = true, features = ["serde"] }
 vite_path = { workspace = true }
 vite_str = { workspace = true }
 vite_workspace = { workspace = true }