Implement E2E tests for the Fellowship salary pallet

[rockbmb]

Context

The Polkadot Technical Fellowship pays its members a monthly salary via pallet-salary (index 64 on Collectives, parachain 1001). The payout is cross-chain: the salary pallet dispatches an XCM message via PayOverXcm to Asset Hub Polkadot, which transfers the salary asset from the pallet's sovereign account to the beneficiary.

PET currently has zero test coverage for the salary pallet.

Salary pallet lifecycle

init -> induct -> [each cycle] bump -> register -> payout -> check_payment
                  |                                |
                  |  RegistrationPeriod (15 days)   |  PayoutPeriod (15 days)
                  +--------------------------------+

Key things to test:

• Induction: a ranked collective member joins the payroll
• Registration: member locks in their salary amount (read from fellowshipCore.params()) within the registration window
• Payout: member claims salary; the pallet dispatches XCM to Asset Hub
• Cross-chain delivery: Asset Hub processes the XCM and transfers the asset to the beneficiary
• Status bookkeeping: fellowshipSalary.status correctly tracks cycle index, budget, registration totals, and paid totals across transitions

Test structure

collectivesPolkadot.salary.e2e.test.ts

"Polkadot Collectives Salary"
+-- "salary lifecycle (raw)"
|   +-- full induct -> register -> payout cycle, no helpers, every step visible
+-- "salary status storage"
|   +-- verify Status storage invariants across cycle transitions
+-- "cross-chain payment"
    +-- salary payout delivers USDT to beneficiary on AssetHub (via payoutOther)

Test approach:

• Real extrinsics for the subject under test; prerequisites seeded via setStorage
• setStorage for time fast-forward (manipulating cycleStart to skip 108k+ blocks)
• Salary params read from chain via fellowshipCore.params() and api.consts.fellowshipSalary.*
• Shared module in packages/shared/src/salary.ts

Validated facts (from runtime source)

• Sovereign account: 13w7NdvSR1Af8xsQTArDtZmVvjE8XhWNdL4yed3iFHrUNCnS -- validated by asset-hub-polkadot xcm_config.rs unit test
• Pallet indices: FellowshipCollective=60, FellowshipCore=63, FellowshipSalary=64
• RegistrationPeriod = PayoutPeriod = 15 x DAYS (DAYS=7200 blocks at 12s block time)
• Budget = 250,000 x USDT_UNITS

[rockbmb]

Scope correction

The original issue conflated two different concerns:

1. Permanent salary pallet E2E coverage (diachronic) - tests the pallet mechanics, belongs in PET, runs on every CI
2. USDT-to-Hollar migration validation (ephemeral) - one-shot verification that the transition works for all current fellows, discarded after migration completes

These should not be mixed. The "Hollar transition prerequisites" tests described in the original issue are the wrong abstraction: they test whether we can seed Hollar infrastructure, not whether the salary flow works with Hollar. After the transition, they become noise in the regression suite.

Revised scope

This issue now covers only (1): permanent salary pallet E2E tests.

Test structure:

collectivesPolkadot.salary.e2e.test.ts

"Polkadot Collectives Salary"
+-- "salary lifecycle (raw)"
|   +-- full induct -> register -> payout cycle, every step visible
+-- "salary status storage"
|   +-- verify Status storage invariants across cycle transitions
+-- "cross-chain payment"
    +-- salary payout delivers USDT to beneficiary on AssetHub

No Hollar-specific tests. The USDT flow is the current production path and what the permanent regression suite should cover.

Migration validation (separate work)

The Hollar transition validation should be standalone tooling, not PET tests:

• Fork live Collectives + AssetHub
• Apply the Hollar runtime upgrade (or inject via storage manipulation)
• Enumerate all current fellows from fellowshipCollective.members
• For each: verify they can complete a salary cycle under Hollar
• Run once, discard after migration succeeds

This is out of scope for this issue. Will be tracked separately if needed.