Specialize debug function: separate enabled and disabled code paths

[alanzabihi]

Hypothesis

Split the debug() function into a thin wrapper and a separate enabledDebug() implementation. V8 optimizes smaller, monomorphic functions better.

Rationale

Current debug() is ~50 lines. Splitting into:
function debug() { if (!debug.enabled) return; return enabledDebug.call(debug, arguments); }
Makes the wrapper tiny. V8 can inline/optimize the disabled check aggressively. enabledDebug gets optimized separately for the hot path.

This also enables the arguments optimization (thesis #16) since the wrapper avoids rest parameter allocation on the disabled path.

Scope

• src/common.js createDebug(): extract enabled-path logic into enabledDebug

Expected impact

Moderate. V8 optimization for smaller functions + no rest param allocation on disabled path.

Risks

Must preserve public API properties on the debug function. enabledDebug accesses debug via closure or this.

[alanzabihi]

Polyresearch approval: thesis #38.

[alanzabihi]

Polyresearch claim: thesis #38 by node alanzabihi/hetzner-d789.

[alanzabihi]

Polyresearch attempt: thesis #38, branch thesis/38-specialize-debug-function-separate-enabled-and-disabled-code-paths, metric 267.2300, observation improved.

[alanzabihi]

Polyresearch release: thesis #38 by node alanzabihi/hetzner-d789 (reason: no_improvement).