Fix run detail page gutters

[federicodeponte]

Closes #2330.

What changed

• Treat only the dedicated /runs/[id] route as a standard page.
• Preserve full-bleed behavior for the /runs collection.
• Add DOM regression coverage for detail, collection, trailing-slash, and standalone share routes.

Root cause

The shell prefix-matched /runs for all descendants, so /runs/[id] inherited the collection shell: no gutters and overflow-hidden.

Verification

• Focused regression: 4/4 passed.
• Full web suite: 1,023 passed, 1 skipped.
• Web lint: passed with existing warnings.
• Web production build: passed.

[federicodeponte]

The required Web lint status is failing in the repository-wide production dependency audit before PR-specific validation. This is reproduced from the unchanged main dependency graph and tracked in #2332. All PR-specific tests, full web tests (1,023 passed), lint, and production build pass locally.