Repoints the vite-task git deps to the tip of the split stack
(voidzero-dev/vite-task#431, the auto-output-track branch), whose crates
tree is identical to the prior pin plus the runner env-change message
refinement. Regenerates the two snapshots whose `VITE_*` cache-miss line
now renders as "envs changed" (matching manual env config) instead of
"tracked env glob 'VITE_*' changed".

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

… command (#436)

## Motivation

The planning context's env map — the full session environment, typically
hundreds of entries — was copied at every boundary it crossed during
planning:

- once into `PlanContext` per plan (`plan_query`),
- once **per `&&`-item** by `PlanContext::duplicate` (each command gets
a scoped context),
- once more per `&&`-item into `ScriptCommand::envs` for program lookup
and plan-request callbacks,
- and once per spawn into `all_envs`.

Of these, only the last one does real work — the spawn env is filtered
in place by `EnvFingerprints::resolve`. Every other copy duplicates an
almost-always-identical map just to hand it to the next stage, and the
cost scales with task count × command count, not with actual env
changes.

The immediate trigger is the upcoming runner-aware caching work
(#430/#431): it saves each spawn's **full env context** into the plan
(`SpawnCommand::full_envs`) so `getEnv`/`getEnvs` and tracked-env
validation resolve against the plan rather than the live process env.
Without sharing, that would add yet another full map copy per spawn;
with this change it costs a pointer.

## Approach

Wrap the map in `Arc` with copy-on-write semantics:

- Duplication and hand-off points (`duplicate`, `ScriptCommand::envs`,
`PlanContext::new`) share the map — O(1).
- The two mutation points pay for a copy only when they change
something: `prepend_path` once per task node (package `.bin` PATH
prepend), and `add_envs` only when a command actually has prefix envs —
an empty prefix set is guarded so it doesn't break sharing.
- The per-spawn `all_envs` clone remains, with a comment marking it as
the one place the map's contents are genuinely copied.

No behavior change; `Session` already held the map in an `Arc`, so its
call sites are untouched.

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>