[WOOMOB-3739] Prepare Product Detail for the Compose cutover (1/3)

[hichamboushaba]

Description

Part 1 of 3. Followed by #16394 and #16395.

Part of WOOMOB-3739 — does not close the ticket.

This is part 1 of 3 in the Product Detail Compose migration stack. It adds the prerequisites without changing the production Product Detail rendering route:

• aligns the shared View-hosted design-system toolbar with the Compose app bar contract, including title metrics, control placement, outlined buttons, and overflow styling;
• preserves persisted Add Product state across restoration and review refreshes; and
• maps legacy Product Detail cards into immutable UI models with stable keys and current callbacks.

The toolbar bridge is reusable by later View-hosted screen migrations. Product-specific Share behavior remains in the final cutover PR.

Test Steps

1. Compare the Compose and XML toolbars in the light image below; verify their height, centered title, control spacing, outlined button geometry, and overflow icon match.
2. Repeat the comparison in the dark image and verify the colors and contrast match.
3. Create and save a product draft, recreate Product Detail after making another edit, and press Back; confirm the restored edit is retained and the discard-changes dialog appears.

Images/gif

Light	Dark

• I have considered if this change warrants release notes and have added them to RELEASE-NOTES.txt if necessary. Use the "[Internal]" label for non-user-facing changes.

[dangermattic]

	1 Warning
⚠️	This PR is larger than 300 lines of changes. Please consider splitting it into smaller PRs for easier and faster reviews.

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[wpmobilebot]

📲 You can test the changes from this Pull Request in WooCommerce Android by scanning the QR code below to install the corresponding build.

	App Name	WooCommerce Android
	Platform	📱 Mobile
	Flavor	Jalapeno
	Build Type	Debug
	Build Number	778
	Version	25.4-rc-1
	Application ID	com.woocommerce.android.prealpha
	Commit	8791976
	Installation URL	5bug7jni7o6oo

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.

[claude]

AI Code Review - No issues found. The changes look good.

The refreshProduct() / restoreStoredProduct() refactor is a solid defensive improvement: it removes the previous unconditional navArgs.mode as ProductDetailFragment.Mode.ShowProduct cast (a latent ClassCastException when refresh ran in the Add flow) and now handles every Mode branch explicitly, guarding against the sentinel DEFAULT_ADD_NEW_PRODUCT_ID. The new ProductDetailUiMapper / ProductDetailUiModel immutable mapping is clean and well covered by unit tests (order preservation, stable/unique keys, callback wiring, snapshot immutability). The WooDesignSystemToolbar visual polish (title font padding, overflow-button outlined styling, vertical centering, border width) is backed by Robolectric tests including RTL. All referenced resources (woo_ds_ic_regular_ellipsis_24dp, woo_ds_toolbar_icon_button_tint) exist.

PR housekeeping

• The new ProductDetailUiMapper and ProductDetailUiModel classes are not yet referenced by any production UI (only by tests) — appears to be intentional scaffolding for a follow-up; just flagging so it isn't left orphaned.
• Applied repo-specific AGENTS.md / CLAUDE.md guidance (store-app MVVM patterns, Kotlin conventions) when reviewing.

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