Document the basis-points fee-rounding convention in the README fee section

[Jagadeeshftw]

📌 Description

quote_fee and open_settlement's fee calculation both use amount * bps / BPS_DENOMINATOR (i128 floor division against a denominator of 10_000), meaning the computed fee always rounds down and can round to 0 for small amounts at low rates — behavior confirmed by quote_fee's own doc comment ("never exceeds the input amount") but not spelled out anywhere in the README for integrators who only read the interface table.

🧩 Requirements and context

• Add a short paragraph to the README's fee-related section explaining the basis-points convention (1 bps = 0.01%), the 10_000 denominator, and the floor-rounding behavior including the zero-fee-at-small-amounts edge case.
• Cross-reference max_fee_bps() as the authoritative source for the current fee cap, avoiding a hardcoded '10%' claim that could drift from MAX_FEE_BPS in src/lib.rs.
• Link to the fee-truncation regression tests (tracked separately in this backlog) as the executable specification of this behavior.

🛠️ Suggested execution

• Add the paragraph to README.md near the existing set_fee/quote_fee/asset_fee table rows.
• No code changes — this is a pure documentation task.
• Keep wording consistent with the doc comments already present in src/lib.rs for quote_fee and set_fee.

✅ Acceptance criteria

• The README explains the basis-points convention, denominator, and floor-rounding behavior in plain language.
• The fee cap is referenced via max_fee_bps() rather than a hardcoded number.
• No functional changes.

🔒 Security notes

Integrators who assume fees round up, or who don't realize a fee can legitimately be zero for a tiny settlement, could build off-chain accounting that mismatches on-chain accrual by a rounding difference that compounds across many small settlements.

📋 Guidelines

• Minimum 95% test coverage
• Clear documentation
• Timeframe: 96 hours

[Ajeey1995]

I’d like to take this issue.

Plan:

1. Verify the fee formula and existing quote_fee/set_fee documentation in src/lib.rs.
2. Add a concise README paragraph beside the fee API rows covering 1 bps = 0.01%, the 10,000 denominator, integer floor rounding, and the legitimate zero-fee edge case for small amounts.
3. Reference max_fee_bps() as the authoritative cap and link the relevant regression-test location without changing code.
4. Run the repository’s documentation/test checks and submit a focused docs-only PR.

I can deliver within one hour after assignment. Before I begin, please confirm the current USDC reward for #159 and whether assignment must be completed through the GrantFox dashboard (or whether this GitHub application is sufficient), so I do not duplicate unassigned work.

[Jagadeeshftw]

Assigned @Ajeey1995 to this issue via repo automation (backfill). Please open a PR referencing this issue (e.g. Closes #159) when you're ready.