Add trustline-removal preconditions to the ChangeTrust example

[Copilot]

The assets skill taught trustline removal as a bare limit: "10000", // 0 to remove trustline comment, omitting the preconditions that make ChangeTrust(limit: 0) succeed: a zero balance, no buying liabilities from open offers, and no liquidity pool references (CAP-0038). It also didn't distinguish an actual trustline from wallet-display or claimable-balance state.

Changes to skills/assets/SKILL.md

• New "Remove Trustline" section documenting the four preconditions:

  1. Identify the asset by code and issuer — display entries and claimable balances are not trustlines and can't be removed via ChangeTrust
  2. Zero the balance (send back to issuer to burn, or elsewhere)
  3. Cancel open offers buying the asset (buying liabilities)
  4. Exit liquidity pool positions referencing the asset (liquidity_pool_use_count > 0 blocks deletion per CAP-0038)

• Example code that pre-checks trustline state before submitting, then maps failures to specific result codes:

  const codes = e.response?.data?.extras?.result_codes?.operations ?? [];
  if (codes.includes("op_invalid_limit")) {
    // CHANGE_TRUST_INVALID_LIMIT: balance or buying liabilities remain
  }
  if (codes.includes("op_cannot_delete")) {
    // CHANGE_TRUST_CANNOT_DELETE: trustline is used by a liquidity pool
  }

• Create-trustline comment now points to the new section instead of the bare "0 to remove" hint

• Trustline Management best practices gain a removal-precondition bullet

Result code strings verified against Stellar's Horizon mapping (ChangeTrustCannotDelete → "op_cannot_delete", ChangeTrustInvalidLimit → "op_invalid_limit").

• Fixes Add trustline-removal preconditions to the ChangeTrust example #81

[Copilot]

Pull request overview

Documents safe trustline removal in the assets skill.

Changes:

• Adds removal preconditions and error handling.
• Updates creation guidance and best practices.

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[kaankacar]

🤖 Automated message from Kaan's Automated Triage Bot.

Verified before merging: the Horizon result-codes reference maps op_invalid_limit ↔ CHANGE_TRUST_INVALID_LIMIT, and the operations reference confirms CHANGE_TRUST_CANNOT_DELETE means the trustline is still referenced by a liquidity pool (CAP-38) — exactly how the new section explains them. The pre-check snippet uses real Horizon balance-line fields and the standard SDK error shape, and the four removal preconditions match protocol behavior. CI is green — merging.

[kaankacar]

Result codes and deletion preconditions verified against the Horizon and operations references.

[kaankacar]

🤖 Automated message from Kaan's Automated Triage Bot.

Both review points were correct and are addressed in #91: the removal guidance now says manageBuyOffer cancels with buyAmount: "0" (verified against the js-stellar-base source), and the preflight snippet notes that pool usage isn't visible on the balance line and surfaces as op_cannot_delete at submit.