Fix escape hatch showing URL instead of page title on cold start

[SabrinaTardio]

Task/Issue URL: https://app.asana.com/1/137249556945/project/1204186595873227/task/1214042008558081?focus=true
Tech Design URL: N/A
CC: N/A

Description

• Preserve the persisted page title in updateTabModel() when the WKWebView title hasn't loaded yet, fixing the escape hatch card showing the URL/domain twice instead of the page title after cold start
• During tab restoration, setting self.url triggers updateTabModel() before WKWebView.title is available via KVO, which overwrites the NSCoding-persisted Link (which has the correct title) with a new Link(title: nil, url:), causing displayTitle to fall back to the host

Testing Steps

1. Open a web page with a visible title (e.g., any news site or booking site)
2. Wait for it to fully load, verify the tab shows the page title
3. Kill the app (swipe away from app switcher)
4. Wait for the idle return threshold to pass
5. Relaunch the app -- verify the NTP escape hatch card shows the page title (not the domain/URL twice)
6. Also verify that navigating to a new page still updates the title correctly (title is not "stuck" on the old one)

Impact and Risks

Impact Level: Low

What could go wrong?

• If a page changes URL without updating the title, the stale title from the previous URL could briefly persist until KVO fires. This is mitigated because updateTabModel() is called again when title changes via its didSet, which will overwrite with the correct value.

Quality Considerations

• The TabViewController.link computed property already performs this same merge logic via Link.merge(with:), so this aligns updateTabModel() with existing behavior
• No privacy or security implications

Notes to Reviewer

• One-line change. The fix mirrors what TabViewController.link (computed property) already does via activeLink.merge(with: storedLink) -- it preserves the existing title when the new one is nil.

Made with Cursor

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Note

Low Risk
Low risk: a small, localized change to how tabModel.link is updated, only affecting tab title persistence when the web view title is temporarily missing during restoration.

Overview
Fixes cold-start tab restoration where updateTabModel() could overwrite a persisted Link title with nil before WKWebView.title is available.

updateTabModel() now keeps the previously stored title for the same URL when the current title is empty, preventing UI surfaces (e.g., the escape hatch card) from showing the URL/domain in place of the page title.

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