fix(ci): avoid Playwright apt installs by using container image

[kitsuyui]

Summary

• run test and octocov jobs in the official Playwright container image (mcr.microsoft.com/playwright:v1.58.2-noble)
• remove pnpm exec playwright install --with-deps from both workflows to avoid long apt execution
• remove the Playwright cache step that became unnecessary after switching to the container image

Why

PR #1557 had a timeout/cancel in test (24.x) while playwright install --with-deps was fetching many Ubuntu packages via apt.
This change avoids that install path entirely.

Related:

• chore(deps): update pnpm to v10.30.1 #1557

Impact

• CI setup time is expected to be more stable and shorter for Playwright-dependent jobs.
• Browser/system dependencies are provided by the container image instead of per-run apt installation.

Validation

• Confirmed workflow diffs for .github/workflows/test.yml and .github/workflows/octocov.yml.
• Local lint/typecheck could not be executed in this environment due to a Corepack signing-key mismatch.

[github-actions]

Code Metrics Report

	main (f0143c6)	#1565 (ce058d4)	+/-
Code to Test Ratio	1:0.6	1:0.6	0.0

Details

  |                    | main (f0143c6) | #1565 (ce058d4) | +/- |
  |--------------------|----------------|-----------------|-----|
  | Code to Test Ratio |          1:0.6 |           1:0.6 | 0.0 |
  |   Code             |           1012 |            1012 |   0 |
  |   Test             |            609 |             609 |   0 |

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Reported by octocov