Improve task runner summary

[yyx990803]

Right now the task runner summary takes up too much screen space:

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    Vite+ Task Runner • Execution Summary
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Statistics:   1 tasks • 0 cache hits • 1 cache misses
Performance:  0% cache hit rate

Task Details:
────────────────────────────────────────────────
  [1] tsdown-behavior#build: $ vp pack index.ts ✓
      → Cache miss: content of input 'vite.config.ts' changed
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

If the user doesn't have the terminal at full window height (e.g. in an IDE terminal, or when the terminal is only taking up a small height at the bottom of the screen), this can easily fill up the entire vertical space, requiring scrolling up to see the original task output.

What we need to do:

• If a single-task run has a cache miss, no need for summary at all.
• For a single-task run with cache hit:

<original output>

---
[vp run] cache hit, 102.96ms saved.

• For multi-task run:

<original output>

---
[vp run] 2/4 cache hit (50%), 1234ms saved. (Run `vp run --details` for full details)

• Running vp run task --details displays the full info directly.
• Running vp run --details displays the full info for the last run.

[linear]

VP-189

[branchseer]

Implemented in voidzero-dev/vite-task#171 and #623.