fix(deploy): persist session key only after map_account confirms on chain (#94)

[EnderOfWorlds007]

Closes #94.

Bug

Session-key creation writes to accounts.json BEFORE the on-chain map_account extrinsic is confirmed. If map_account fails (race-induced Stale nonce, network blip, etc), the local file says "key created" but the chain has no mapping. Retries find the existing key (created=false), skip the mapping step, and dry-run fails with Revive::AccountUnmapped.

Fix

Split create-from-or-load-disk from persist-to-disk. The deploy flow now:

1. getOrCreateSessionAccount — returns key (created in-memory if new, loaded from disk if existing). Does NOT write to disk.
2. If created: map_account extrinsic — fail loudly here if anything goes wrong, no on-disk side effect.
3. persistSessionAccount — write to disk only AFTER mapping confirmed.

Failures between (1) and (3) leave the on-disk state untouched, so retries treat it as a fresh create and re-map.

Implementation notes

• InMemoryKvStore added to session-account.ts to back SessionKeyManager.create() without touching the filesystem.
• persistSessionAccount(info) exported from session-account.ts — writes the mnemonic under the "default" key, same shape as before.
• run.ts updated: persistSessionAccount called immediately after submitAndWatch(map_account()) returns, inside the if (created) branch.
• Direct migration — only one real caller (run.ts); no back-compat wrapper needed.

Test plan

• getOrCreateSessionAccount fresh call: valid key returned, file absent
• getOrCreateSessionAccount → persistSessionAccount: file written with correct mnemonic
• getOrCreateSessionAccount after persist: created=false, same mnemonic loaded
• map_account-fails scenario: no persist → retry returns created=true with different key → retry would re-map
• Garbage-in-store scenario: fresh key minted, garbage file not overwritten
• All 450 existing unit tests pass

[github-actions]

Dev build ready — try this branch:

curl -fsSL https://raw.githubusercontent.com/paritytech/playground-cli/main/install.sh | VERSION=dev/fix/session-persist-after-map bash

[github-actions]

E2E Test Pass · ✅ PASS

Tag: e2e-ci-pr · Branch: fix/session-persist-after-map · Commit: 00a7bb1 · Run logs

Cell	Result	Time
pr-deploy-foundry	✅ PASS	2m30s
pr-install	✅ PASS	0m37s
pr-deploy-frontend	✅ PASS	6m45s
pr-init-session	✅ PASS	1m22s
pr-preflight	✅ PASS	2m14s
pr-mod	✅ PASS	1m19s
${{ matrix.cell }}	⏭️ SKIP	0m00s
${{ matrix.cell }}	⏭️ SKIP	0m00s

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