feat(cct-sdk): Add accept admin solana op

[mervin-link]

What

• DAPP-10605
• Add Solana CCT acceptAdmin and generateUnsignedAcceptAdmin TokenAdminRegistry operations
• Validate current pending authority before building acceptAdminRoleTokenAdminRegistry

Why

• Enable pending TokenAdminRegistry administrators to accept the role through the SDK

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[aelmanaa]

I ran this op live on Solana devnet from an isolated build:

• deployToken 3NSLt4D1…c77KW→ deployTokenPool → createLookupTable → registerToken(owner) 2EaqH4xV…rCrs (registry: administrator = zero default, pending = wallet) → acceptAdmin 2Uendc85…bQiX → setPool succeeds 2UqWZfap…VS3U — the exact call that reverted Unauthorized (7000) in the register-token review before this op existed.
• Wire-exact: the landed instruction data is exactly 6af010ad89d5a3f6 = sha256(global:accept_admin_role_token_admin_registry)[0..8], no args; program log Instruction: AcceptAdminRoleTokenAdminRegistry; accounts (config RO, registry writable, mint RO, authority signer+writable) match the canonical AcceptAdminRoleTokenAdminRegistry context (token_context.rs:179-196) and what ccip-solana-bs58-generator's accept-admin-role builds. Read the registry PDA back two independent ways (SDK decode + raw borsh-offset decode): administrator == wallet, pending zeroed — the handler's exact promotion semantics (token_admin_registry.rs:115-132).
• Both accept paths proven: accept-after-register (admin = zeros) and accept-after-transfer (admin non-zero, via a self-proposeAdmin then a second accept, tx oEExtfeJ…Vb8n) — the preflight gates on pending == authority only, exactly like the chain (never stricter, never looser), and the registry's lookup_table survives the accept untouched, as the handler promises.
• Isolation semantics are right and typed, client-side before any tx: unregistered mint → CCIPTokenNotConfiguredError; no pending / wrong wallet → CCTParamsInvalidError. Notably better than our bs58 generator, which has no preflight at all for this op.
• Naming: 👍. acceptAdmin is the one op of the trio that already matches the agreed cross-family scheme (registerAdmin / transferAdmin / acceptAdmin) — nothing to rename here.

Two asks before merge, both raised inline with suggestions: A1 (the "no pending admin" test rejects via the wrong branch — proven with a sentinel-message experiment at this head) and A3 (one message for two different rejection states; the idempotent-retry case reads wrong — hit it live). On stacking: since #313 will rename proposeAdmin → transferAdmin on the base branch, and this PR's added lines never reference the propose op, the rename only shuffles adjacent import/barrel lines — landing order #313-rename → #317 keeps both merges trivial. 5/5 new tests pass at the merged form on my machine.

[aelmanaa]

Re-reviewed at 0429741 (was 0a53a3c). 6 of 7 prior comments are fixed — thank you. One trivial blocker remains: the "no pending admin" test assertion substring doesn't match the message text, so accept-admin.test.ts fails 1/5.

Fixed at 0429741:

• A3 (conflated message) ✅ — two distinct messages at accept-admin.ts:69-82, both live-proven on devnet
• Address docstring ✅ — trimmed to "Router or OffRamp"
• Test typing ✅ — Partial<GenerateAcceptAdminParams>
• Discriminator + account-metas assert ✅ — 6af010ad89d5a3f6 + full key flags
• Execute-path reason assert ✅ — includes('requires authority to be the executing wallet')
• Journey docs ✅ — @remarks/@see to registerAdmin/transferAdmin/setPool on both facade methods

Remaining (inline): the A1 stub fix is structurally correct (now reaches the !pendingAdministrator branch), but the assertion checks reason.includes('no pending administrator') while the message reads "no administrator is pending for this token…" — word order is swapped, substring doesn't match, test is RED. One-word fix: align the assertion to 'no administrator is pending' or 'nothing to accept'.