Fix compilation when tracing feature is disabled

[Copilot]

DiskANN 0.45.0 fails to compile with --no-default-features because tracing macros unconditionally reference the tracing crate.

Changes

diskann/src/tracing.rs

• Added #[cfg(feature = "tracing")] guards to all macro definitions
• Provided no-op implementations when feature is disabled:

  #[cfg(not(feature = "tracing"))]
  #[macro_export]
  macro_rules! tracked_error {
      ($($arg:tt)+) => {{}};
  }

• Added stub debug! and trace! macros that expand to empty blocks
• Re-export actual tracing::{debug, trace} when feature is enabled

diskann/src/graph/index.rs

• Changed import from use tracing::{debug, trace} to use crate::tracing::{debug, trace}
• Routes all tracing macro usage through the conditional implementations

Original prompt

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This section details on the original issue you should resolve

<issue_title>[BUG] DiskANN 0.45.0 needs the tracing feature.</issue_title>
<issue_description>DiskANN version 0.45.0 does not compile if the tracing feature is disabled.</issue_description>

<agent_instructions>The macros in diskann/src/tracing.rs should compile to nothing if the tracing feature is not enabled. This should be a relatively simple change, but we need to expand our CI testing to ensure that our crates properly build with no features enabled.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes [BUG] DiskANN 0.45.0 needs the tracing feature. #720

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[hildebrandmw]

Closing in favor of #722 .