spec(errata): §2.2.1 USD=USDC clarification + fixture address realism (audit-A H2/M9)

Closes audit-A residual findings on the spec side.

A-H2 (HIGH) — spec/06-x402-integration.md new §2.2.1
  Documents that for v1.1.0, amount_usd is the same value as the
  x402 USDC amount divided by 10^6 — no Stripe processing fee uplift.
  Wallet path is pre-funded by Stripe with fees already absorbed.
  Removes ambiguity around sub-cent precision (amount_usd: 0.005
  is canonical for a 5,000-micro USDC invoice).

A-M9 (MEDIUM) — fixtures/x402-happy-path-pure.json
  Replaced placeholder addresses that failed the strict 40-hex regex:
    0xAAAA…AAA1  (41 chars)  -> 0xAaaAaAAaaAaAAaaAaAaAAaaAaAaAAaaAaAaAAaAa
    0xSPLITTER…01234 (non-hex) -> 0x000000000000000000000000000000000000C0DE
  Regenerated base64 X-Payment + X-Payment-Response headers to match.
  Other 2 fixtures (error-payment-invalid, error-not-accepted) had
  0xabc... strings inside narrative messages, not address fields —
  left intact.

Companion commit:
  JobDoneBot cf17aed   Hub + SDK side of audit-A residual sweep

Author: tufedev

fixtures/x402-happy-path-pure.json

@@ -12,7 +12,7 @@
       "Content-Type": "application/json",
       "X-Agent-ID": "jdb_ag_x402test_happy_001",
       "X-API-Key":  "jdb_ak_xxxxxxxxxxxxxxxxxxxxx",
-      "X-Payment":  "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"
+      "X-Payment":  "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"
     },
     "body": {
       "jecp": "1.0",
@@ -30,8 +30,8 @@
     "payload": {
       "signature": "0x1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef12345678",
       "authorization": {
-        "from":        "0xAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA1",
-        "to":          "0xSPLITTER000000000000000000000000000001234",
+        "from":        "0xAaaAaAAaaAaAAaaAaAaAAaaAaAaAAaaAaAaAAaAa",
+        "to":          "0x000000000000000000000000000000000000C0DE",
         "value":       "200000",
         "validAfter":  "1762689600",
         "validBefore": "1762689660",
@@ -44,7 +44,7 @@
     {
       "endpoint": "/verify",
       "request_body": { "x402Version": 1, "paymentPayload": "<echoes decoded>", "paymentRequirements": "<from challenge>" },
-      "response_body": { "isValid": true, "invalidReason": null, "payer": "0xAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA1" }
+      "response_body": { "isValid": true, "invalidReason": null, "payer": "0xAaaAaAAaaAaAAaaAaAaAAaaAaAaAAaaAaAaAAaAa" }
     },
     {
       "endpoint": "/settle",
@@ -54,7 +54,7 @@
         "errorReason": null,
         "transaction": "0xc0ffee0000000000000000000000000000000000000000000000000000000001",
         "network": "base",
-        "payer": "0xAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA1"
+        "payer": "0xAaaAaAAaaAaAAaaAaAaAAaaAaAaAAaaAaAaAAaAa"
       }
     }
   ],
@@ -64,7 +64,7 @@
     "headers": {
       "Content-Type": "application/json",
       "Cache-Control": "no-store",
-      "X-Payment-Response": "eyJzdWNjZXNzIjp0cnVlLCJ0cmFuc2FjdGlvbiI6IjB4YzBmZmVlMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAxIiwibmV0d29yayI6ImJhc2UiLCJwYXllciI6IjB4QUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUExIn0=",
+      "X-Payment-Response": "eyJzdWNjZXNzIjp0cnVlLCJ0cmFuc2FjdGlvbiI6IjB4YzBmZmVlMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMSIsIm5ldHdvcmsiOiJiYXNlIiwicGF5ZXIiOiIweEFhYUFhQUFhYUFhQUFhYUFhQWFBQWFhQWFBYUFBYWFBYUFhQUFhQWEifQ==",
       "Access-Control-Expose-Headers": "X-Payment-Response, X-Request-Id"
     },
     "body": {
@@ -83,7 +83,7 @@
         "x402": {
           "settlement_tx": "0xc0ffee0000000000000000000000000000000000000000000000000000000001",
           "network": "base",
-          "payer": "0xAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA1",
+          "payer": "0xAaaAaAAaaAaAAaaAaAaAAaaAaAaAAaaAaAaAAaAa",
           "facilitator": "https://x402.org/facilitator"
         }
       },

spec/06-x402-integration.md

@@ -113,6 +113,10 @@ WWW-Authenticate: x402 realm="jecp.dev", network="base", asset="USDC"
 | `WWW-Authenticate` header | SHOULD | Standard HTTP challenge per RFC 7235. Allows non-JSON-aware clients to surface the requirement. |
 | `Cache-Control: no-store` | MUST | Prevents CDN caching of paid challenge responses. |
 
+#### 2.2.1 `amount_usd` semantics on `stripe-wallet` entries
+
+When both `stripe-wallet` and `exact` (x402) entries are emitted for the same action, the `stripe-wallet` entry's `amount_usd` and the `exact` entry's `max_amount_required` (atomic USDC) reference the **same underlying price**. For v1.1.0, USD ≡ USDC at 1:1 — the `amount_usd` value is `max_amount_required ÷ 10^6` exactly, with no Stripe processing-fee uplift. Rationale: the wallet path is pre-funded via Stripe (top-up flows absorb the fee at top-up time), so per-call billing does not re-charge for fees. Hubs MUST serialize `amount_usd` with up to 6 decimal places so sub-cent prices (e.g., `$0.005` = `5000` micro-USDC) round-trip cleanly through JSON; clients MUST NOT cast to integer cents. A future v1.2 MAY introduce per-call fee uplift; if so, the relationship between the two amounts will be redefined under a new field — the v1.1.0 invariant is "same value, different unit."
+
 ### 2.3 `accepts[]` order
 
 When both `stripe-wallet` and `exact` (x402) entries are present, the Hub MUST list `stripe-wallet` first. Rationale: Stripe is more recoverable (chargeback / dispute paths exist). This is a normative requirement to mitigate mode-confusion attacks (Panel 2 TM-MC: agents that misinterpret order may consume the wrong signed authorization). x402-native positioning lives in marketing surfaces, not in protocol field order.