t27b ratchet: specs/policy/own_language.t27 regressed to ExprCall(@intCast) with #7399 #7478

Part of #6063.

Since #7399 (3df7065), specs/policy/own_language.t27 contains @as(u32, @intCast(c - '0')) at line 411, in the code that parses git diff --numstat for check_budget. t27b refuses @intCast, so this spec, which the ledger lists as pass, now stops at ExprCall(@intCast).

Every PR's t27b-native-ratchet therefore reports UNEXPECTED FAILURE 1. Two runs show it:

• the lab corpus on 3df7065;
• CI run 37603940540 on t27b: frames over 16 KiB, probing the stack one page at a time (Closes #7367) #7425.

Lane 5 found this while running the corpus for #7448. It is not a lane 5 blocker: @intCast belongs to lane 4, and a ledger move belongs to lane 2. So lane 5 does not touch the row.

Two ways out:

• t27b gains @intCast (lane 4).
• The spec avoids it, e.g. a u32 digit from c - '0' where c is already a u8. That is a spec change, which must keep t27c test-report and gen-c output identical for check_budget.

Boundary

• specs/policy/own_language.t27

User Scenarios

• Given specs/policy/own_language.t27 contains @as(u32, @intCast(c - '0')) at line 411, when t27b-native-ratchet runs on this spec, then it stops at ExprCall(@intCast) and reports UNEXPECTED FAILURE 1.
• Given the spec is changed to avoid @intCast while preserving the u32 digit computation from c - '0' where c is a u8, when t27b-native-ratchet runs, then the spec passes without ExprCall(@intCast) errors.
• Given the modified spec is compiled with t27c test-report and the generated C output for check_budget is produced, then both are identical to the current outputs before the change.

Requirements

• FR-001: The spec specs/policy/own_language.t27 MUST replace @as(u32, @intCast(c - '0')) with an equivalent expression that does not use @intCast.
• FR-002: The replacement expression MUST compute a u32 digit value from c - '0' where c is a u8.
• FR-003: The change MUST keep t27c test-report output identical for check_budget.
• FR-004: The change MUST keep gen-c output for check_budget identical.

Success Criteria

• t27b-native-ratchet runs on specs/policy/own_language.t27 and exits with exit 0 (no UNEXPECTED FAILURE).
• t27c test-report specs/policy/own_language.t27 produces identical output to the pre-change baseline (verified by diff, 0 differences).
• gen/c/policy/own_language.c for the check_budget function is byte-for-byte identical to the pre-change baseline (verified by diff, 0 differences).