fix(dot init): stop double-deriving the product account; key username on wallet root

[UtkarshBhardwaj007]

Summary

Follow-up to #185. Three coupled bugs in dot init's identity block, surfaced when comparing the CLI's output to the playground-app's [playground.dot] selected account log and to the mobile app's developer-tools debug screen.

1. Stop double-deriving the product account

IdentityLines called productAccountDisplay(loggedInAddress). loggedInAddress was already the product account (the output of createPlaygroundSessionSigner.publicKey). The helper ss58-decoded it and ran deriveProductAccountPublicKey a second time, producing a doubly-derived ghost address whose H160 didn't match what the playground-app uses.

Fix: a SessionAddresses = { rootAddress, productAddress, productH160 } triple is computed once in auth.ts::deriveSessionAddresses via a new shared helper derivePlaygroundProductPublicKey in sessionSigner.ts. Both the signer constructor and the display now go through the same function, so they can't drift.

Verified end-to-end against the playground-app's log for the test mnemonic train snow there sponsor artwork zebra gossip depth narrow blame change private:

	Playground-app log	CLI (after fix)
product address	5GGpUaN7XNaUp3nEVDPBSR4SQLxFxQsiPHbFwf69Apr3HgDZ	matches
product derivedH160	0x47f68a0851a663dfacb4610d673ec708f05576b0	matches

Frozen-vector regression test in src/utils/auth.test.ts::deriveSessionAddresses locks the contract — three tests: known-vector match, product != root, and H160 moves in lock-step with the product SS58 when the root changes.

2. Username lookup keyed on the wallet root

lookupUsername was being called with the product account. Usernames live at Resources.Consumers[<rootAccountId>] on the People parachain — mobile's Resources.register_person writes them keyed on the SSO rootAccountId. Polkadot-desktop's useSessionIdentity(session) reads the same root key. IdentityLines now calls lookupUsername(addresses.rootAddress).

3. "logged in" label

The row used to show the product account, which the user reasonably expects to be their wallet identity. It now shows addresses.rootAddress (the SSO-handshake rootUserAccountId). The product account is on its own row underneath with the full SS58 + H160.

This still won't match what the mobile app shows as "Wallet account address" on its debug screen (hard //wallet junction; the host can't reach it from a public key alone) — but it does match what the SSO handshake actually transmits and is the storage key the username lookup uses.

What the user sees now

✓ logged in       5FZEMcMGTjSveipHTD35RsRtMqZf2wk41g2zAPL8j2UwWTrp
✓ username        alice.dot    (or "(no username set on chain)")
✓ product account 5GGpUaN7XNaUp3nEVDPBSR4SQLxFxQsiPHbFwf69Apr3HgDZ (0x47f68a0851a663dfacb4610d673ec708f05576b0)

Documentation

CLAUDE.md gets a new "Accounts: root, product, and what the mobile app shows" section under "Non-obvious invariants" so the next maintainer can re-verify the host-vs-mobile derivation map without re-reading host-papp's handshake codec.

Mechanical changes

• src/utils/sessionSigner.ts: export derivePlaygroundProductPublicKey(rootAccountId, ref) — single source of truth for product-account math.
• src/utils/auth.ts: new SessionAddresses type + deriveSessionAddresses(session) helper. ConnectResult.existing, LoginStatus.success, and SessionHandle carry the bundle. SessionHandle.address kept as a back-compat alias.
• src/commands/init/IdentityLines.tsx: take SessionAddresses, render three rows, look up username against root.
• src/commands/init/InitScreen.tsx: track addresses instead of loggedInAddress. The "logged in" row now lives inside IdentityLines only.
• src/commands/init/QrLogin.tsx: pass full SessionAddresses through onDone; suppress the duplicate "logged in" row on success.
• src/commands/init/index.ts: rename existingAddress → existingAddresses.
• src/commands/init/identityLine.ts + identityLine.test.ts: deleted. The helpers encoded the exact wrong shape and have no remaining callers.

Test plan

• pnpm format:check (145 files clean)
• pnpm lint:license (172/172 files)
• pnpm test — 536 passed, 1 skipped (added 3 new regression tests in the deriveSessionAddresses block)
• Live derivation match against the playground-app's published log for the test mnemonic
• Manual dot init post-merge: confirm three rows render with full root + product SS58 + H160; confirm username lookup completes against the root (returns (no username set on chain) for accounts that haven't claimed one, otherwise the actual username)

[github-actions]

E2E Test Pass · ✅ PASS

Tag: e2e-ci-pr · Branch: fix/dot-init-account-derivation · Commit: 7cd286f · Run logs

Cell	Result	Time
pr-deploy-cdm	✅ PASS	2m34s
pr-mod	✅ PASS	2m00s
pr-preflight	✅ PASS	2m54s
pr-install	✅ PASS	0m53s
pr-init-session	✅ PASS	1m51s
pr-deploy-frontend	✅ PASS	3m13s
pr-deploy-foundry	✅ PASS	1m09s
${{ matrix.cell }}	⏭️ SKIP	0m-1s
${{ matrix.cell }}	⏭️ SKIP	0m-1s

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