feat(registry): overflow-safe math sweep and hardened error paths

[Paranoa-dev]

Summary

Replaces all raw arithmetic in the Callora Registry contract with overflow-safe checked operations and eliminates unwrap_or() from production code paths.

Changes

contracts/registry/src/lib.rs

• Replace .unwrap_or(0) with .ok_or(RegistryError::NotInitialized)? on RegisteredCount reads in register_offering(), register_offering_with_gate(), and registered_count(). This removes silent fallback-to-zero that could mask initialization bugs and aligns with the "no unwrap() in production paths" guideline.
• The existing checked_add(1).ok_or(RegistryError::Overflow)? pattern on the count increment is preserved (was already correct).

contracts/registry/tests/overflow_safe.rs (new â�� 15 tests)

Test	What it verifies
register_offering_count_overflow_returns_error	u32::MAX count � RegistryError::Overflow
register_offering_with_gate_count_overflow_returns_error	Same overflow on gated path
overflow_does_not_persist_offering_record	No partial state after overflow
register_offering_increments_count	Count increments 0�1�2
register_offering_with_gate_increments_count	Count increments via gated path
balance_gate_exact_match_allows_registration	balance == min_balance succeeds
balance_gate_one_below_min_rejects	balance < min_balance � InsufficientDeveloperBalance
init_requires_auth	init rejects unauthenticated callers
register_offering_requires_caller_auth	register_offering rejects unauthenticated callers
register_offering_with_gate_requires_caller_auth	register_offering_with_gate rejects unauthenticated callers
registered_count_does_not_require_auth	Read-only; no auth needed
is_offering_registered_does_not_require_auth	Read-only; no auth needed
registered_count_before_init_returns_not_initialized	Pre-init query � NotInitialized
duplicate_offering_registration_rejected	Duplicate � OfferingAlreadyRegistered, count unchanged
non_admin_register_offering_returns_unauthorized	Non-admin caller � Unauthorized

contracts/registry/tests/xcontract.rs

• Fix method name try_register_offering_with_balance_gate â�� try_register_offering_with_gate
• Fix error matching pattern Ok(Err(...)) â�� Err(Ok(...)) to match correct Soroban try_* return type

Cargo.toml

• Add contracts/registry and contracts/hot to workspace members

Test Results

running 2 unit tests � ok
running 15 overflow_safe tests � ok
running 7 xcontract tests � ok
Total: 24/24 passing

Overflow Safety Audit

Operation	Location	Safety mechanism
Count increment	lib.rs:137,203	checked_add(1).ok_or(RegistryError::Overflow)?
Count read	lib.rs:132,198,234	.ok_or(RegistryError::NotInitialized)? (no unwrap_or)
Balance comparison	lib.rs:176	i128 comparison, no arithmetic
Length checks	lib.rs:77,84	u32 comparison, no arithmetic

Checklist

• Overflow-safe math; no unwrap() in production paths
• require_auth on every state-changing entrypoint
• 24 tests passing (unit + integration)
• NatSpec-style /// rustdoc on all public functions
• No new public entrypoints introduced

Closes #746

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