Conformance rules for navigation timings and page-level assertion targets #479

Part of #278.

Two bugs fixed this week were caught by review rather than by the conformance suite, because no rule covers them:

1. Navigation rows carry performance timings. Core's capture script never returned its payload, so the WDIO service, Selenium and Nightwatch attached no timings to any navigation row (fix: read navigation performance timings without breaking Nightwatch commands #467). The capability matrix marks "Performance timings on navigation rows" as checked by hand for those three adapters.
2. An assertion on a page-level value names no element. assert.notEqual(await driver.getTitle(), 'Welcome') boxed an element whose earlier read returned 'Welcome' (fix(core): name no target when an assert's subject belongs to no element #476, and the Python equivalent in Give Python assertion rows the element their value was read from #475).

Proposal

• Have the fake browser answer the performance script with a navigation entry, and add a rule that every navigation row eventually carries performance (after its replaceCommand).
• Add a scenario step where a title read and an element read return the same text, assert on the title, and add a rule (or agreement field) that the assertion row carries no selector.
• Back the "Performance timings" cells in packages/conformance/src/features.ts with the new rule, regenerate the tables, and mirror them to the docs site.

Acceptance

• Both rules fail on a build with fix: read navigation performance timings without breaking Nightwatch commands #467 or fix(core): name no target when an assert's subject belongs to no element #476 reverted, and pass on main.
• The performance-timings row reads "tested" for every adapter that passes it.