fix(eliminate): skip inlining when free vars in Init are moved before substitution site

[NikolaRHristov]

Fixes #56.

Problem

A candidate like:

let path_display = path.clone();
client.get_file_info(Request::new(FileInfoRequest { request_id, path })).await?;
devlog!("{}", path_display, path.clone());

passed every existing safety check (count=1, not-in-closure, not-unsafe, not-oversized) and was inlined. The result placed path.clone() inside the devlog! macro token stream after path had already been moved by value into FileInfoRequest, producing E0382.

Fix

Safe.rs

Adds IsFreeVarSafe(Init, StmtsBetween). It:

1. Walks Init with FreeIdentCollector to collect all plain single-segment identifier free variables.
2. For each, scans StmtsBetween with MoveDetector which flags a by-value use of that identifier in a call argument, struct field, let RHS, or assignment.
3. Returns false if any free variable is found to be moved.

MoveDetector deliberately skips &/&mut reference expressions (borrows, not moves) and method-call receivers (almost always borrowed self).

Inline.rs

Adds FindSubstSite(Stmts, Target) which returns the index of the first statement in StmtsAfter that contains a reference to the candidate. This bounds the StmtsBetween slice to only the statements that execute between the declaration and the substitution point.

EliminateBlock now calls IsFreeVarSafe(&Candidate.Init, StmtsBetween) after the count check and before SubstituteRef. A false result skips the candidate.

Tests added

• Safe::Tests::FreeVarUnsafeWhenMovedIntoStructField - struct field shorthand moves the var
• Safe::Tests::FreeVarUnsafeWhenMovedIntoCall - by-value function argument
• Safe::Tests::FreeVarSafeWhenVarOnlyBorrowed - reference: not a move
• Safe::Tests::FreeVarSafeWhenDifferentVarMoved - unrelated var moved, target is safe
• Safe::Tests::FreeVarUnsafeWhenMovedIntoRpcRequest - exact AirClient pattern
• Inline::Tests::DisplayCloneKeptWhenOriginalMovedFirst - get_file_info regression
• Inline::Tests::SectionDisplayCloneKeptWhenOriginalMovedFirst - get_configuration regression
• Inline::Tests::DisplayCloneInlinedWhenOriginalNotMoved - false positive guard