feat: add ephemeral flag

[bmuddha]

Summary by CodeRabbit

• New Features

  • Added ephemeral flag support for accounts with public methods to set and read ephemeral status.

• Tests

  • Added a comprehensive test suite verifying copy-on-write account behavior, serialization, ownership transitions, flag persistence, and rollback scenarios.

• Documentation

  • Debug output updated to include ephemeral flag state.

• Chores

  • Manifest formatting cleaned up (non-functional).

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[coderabbitai]

Walkthrough

Adds an ephemeral flag to AccountSharedData (EPHEMERAL_FLAG_INDEX) with getter/setter and Debug output, exposes ACCOUNT_STATIC_SIZE, moves and expands tests into a new crate-level tests module, removes an internal test module from cow.rs, and applies non-functional formatting to Cargo.toml.

Changes

Cohort / File(s)	Summary
Build configuration Cargo.toml	Formatting-only edits to feature lists and consolidation of frozen-abi feature; removed commented patch.crates-io block. No functional dependency changes.
Cow internals & constants src/cow.rs	Added EPHEMERAL_FLAG_INDEX (pub(crate) const), added RELATIVE_DATA_LEN_POINTER_OFFSET_TEST (pub(crate)), removed RELATIVE_DATA_CAP_POINTER_OFFSET, changed ACCOUNT_STATIC_SIZE visibility to pub, and removed the file-local #[cfg(test)] test module.
Library API & behavior src/lib.rs	Re-exported EPHEMERAL_FLAG_INDEX, added pub fn set_ephemeral(&mut self, ephemeral: bool) and pub fn ephemeral(&self) -> bool on AccountSharedData, extended Debug output to include ephemeral state, and added a crate-level #[cfg(test)] mod tests;.
Tests — CoW behavior src/tests.rs	New comprehensive CoW test suite exercising layout/serialization, borrow→own transitions, shadow-switch commit/rollback, data ops, and flag persistence (including ephemeral).

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• feat: add lamports modification marker & refactor #27: Modifies account flag/marker handling and CoW behavior in the same modules (src/cow.rs, src/lib.rs).

Suggested reviewers

• thlorenz

🚥 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 change: adding an ephemeral flag to the codebase. This is evident from EPHEMERAL_FLAG_INDEX constant additions, new ephemeral() and set_ephemeral() methods, and comprehensive test coverage for the ephemeral flag feature across multiple files.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch bmuddha/feat/ephemeral-flag

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[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@src/lib.rs`:
- Around line 43-44: The build fails because the declared test module mod
cow_tests; in lib.rs has no corresponding src/cow_tests.rs or
src/cow_tests/mod.rs; either add the missing test file containing the cow_tests
module (with its tests) or remove the stray declaration from lib.rs (the line
"mod cow_tests;") to resolve the E0583 error; locate the declaration in lib.rs
and perform one of those two fixes depending on whether the tests were moved or
omitted.

[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@src/lib.rs`:
- Around line 43-44: There is a duplicate tests module: the new external
declaration `mod tests;` conflicts with the existing inline `#[cfg(test)] pub
mod tests { ... }`; fix by removing or renaming the inline module (e.g., change
`pub mod tests` to `pub mod inline_tests` or move its contents into the new
`src/tests.rs`) and ensure only one `tests` module exists, keeping the external
`mod tests;` as the canonical test module while updating any test references
accordingly.