fix: revert encrypt workaround after Poulpy prepare fix

[cedoor]

• Bump poulpy to rev 067fd785; encrypt via FheUint::encrypt_sk + glwe enc infos
• Drop prepared cache on Ciphertext; eval_binary prepares operands with fhe_uint_prepare_tmp_bytes
• Size scratch from Poulpy *_tmp_bytes for encrypt, decrypt, keygen, and each homomorphic op
• encrypt now takes (value, sk) only; update README, example, and tests
• Mark milestone issue refactor: revert encrypt workaround once upstream poulpy bug is fixed #24 done in README

Summary by CodeRabbit

• API Changes

  • Simplified encrypt() method signature—evaluation key parameter no longer required, streamlining encryption calls.

• Improvements

  • Streamlined internal ciphertext handling by eliminating cached intermediate state.
  • Completed upstream dependency workaround integration.

• Documentation

  • Updated usage examples and README to reflect simplified encryption API.

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 430a5447-6597-46f4-b6b1-251586aa5c6c

📥 Commits

Reviewing files that changed from the base of the PR and between 20015a7 and 346ca90.

⛔ Files ignored due to path filters (1)

• Cargo.lock is excluded by !**/*.lock

📒 Files selected for processing (9)

• Cargo.toml
• README.md
• examples/add_u32.rs
• src/ciphertext.rs
• src/context.rs
• tests/bdd_parallel.rs
• tests/ciphertext_serialization.rs
• tests/evaluation_key_serialization.rs
• tests/keygen_seeds.rs

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📝 Walkthrough

Walkthrough

Cargo.toml dependencies updated to specific poulpy commit revisions. The codebase removes the cached "prepared" ciphertext mechanism from Ciphertext, changes Context::encrypt to no longer require an EvaluationKey parameter, and refactors eval_binary to rebuild FheUintPrepared operands on-demand during operations. All examples and tests are updated accordingly.

Changes

Cohort / File(s)	Summary
Dependency Updates Cargo.toml	Updated poulpy-* dependency revisions to 067fd785a1d9087f7d9fa437a8503a2d74ac737f.
Public API Signature Changes src/context.rs	Changed encrypt signature to remove EvaluationKey parameter; rewrote eval_binary to rebuild FheUintPrepared operands on each call instead of relying on cached prepared state; adjusted imports for new preparation flow.
Struct Field Removal src/ciphertext.rs	Removed prepared: Option<FheUintPrepared<...>> field from Ciphertext<T>; updated module-level documentation to reflect that prepared state is no longer cached or exposed.
Documentation & Examples README.md, examples/add_u32.rs	Updated code examples and usage documentation to reflect new encrypt signature (removed EvaluationKey argument); marked related roadmap item as completed.
Test Updates tests/bdd_parallel.rs, tests/ciphertext_serialization.rs, tests/evaluation_key_serialization.rs, tests/keygen_seeds.rs	Consistently updated all test encryption calls to use new signature without EvaluationKey parameter.

Sequence Diagram(s)

sequenceDiagram
    actor User
    participant Context
    participant Ciphertext as Ciphertext<br/>(packed only)
    participant Backend as Backend<br/>(eval_binary)
    
    rect rgba(100, 200, 100, 0.5)
    Note over User,Backend: NEW FLOW: On-demand preparation
    User->>Context: encrypt(value, &sk)
    Context->>Ciphertext: new (inner only)
    Ciphertext-->>User: Ciphertext<T>
    
    User->>Context: add(&ct_a, &ct_b, &ek)
    Context->>Context: rebuild FheUintPrepared from ct_a.inner
    Context->>Context: rebuild FheUintPrepared from ct_b.inner
    Context->>Backend: eval(prepared_a, prepared_b)
    Backend-->>Context: result (packed)
    Context->>Ciphertext: new (inner only)
    Ciphertext-->>User: Ciphertext<T>
    end

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related issues

• refactor: revert encrypt workaround once upstream poulpy bug is fixed #24: Directly implements the revert of the encrypt workaround by removing Ciphertext::prepared field, changing Context::encrypt signature to drop EvaluationKey, and rebuilding FheUintPrepared inside eval_binary on-demand.

Possibly related PRs

• feat: add secret and evaluation key serialization #23: Modifies overlapping code paths including Context::encrypt signature, Ciphertext prepared-cache field, and the eval/prepare preparation flow, creating potential code-level conflicts.

Poem

🐰 Prepared caches, now set free!
No more storing what we see,
Rebuild on demand, sleek and light,
The workaround takes its flight! ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately reflects the main objective of this PR: reverting the encrypt workaround now that Poulpy's underlying prepare bug has been fixed.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing Touches

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• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch refactor/revert-workaround

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