Encode track entry links in Asset Pricing index

The Asset Pricing landing page was linking to subpages with raw spaces in the target path, which is fragile in the rendered book and easy to break in different viewers. This change switches those entry links to percent-encoded paths so the chapter pages open consistently.

Constraint: keep the landing page simple and avoid changing the underlying note structure
Rejected: replace the links with wiki-style aliases | the book renderer already handles encoded markdown links more predictably here
Confidence: high
Scope-risk: narrow
Directive: when linking into spaced folder names from book pages, use encoded markdown targets
Tested: verified the landing page no longer contains raw-space link targets
Not-tested: full site render after the link encoding change
Co-authored-by: OmX <omx@oh-my-codex.dev>

Author: Yuning598

book/Asset Pricing/index.md

@@ -3,7 +3,7 @@ This section collects the theoretical and empirical asset pricing notes.
 
 ## By track
 
-- [Empirical Asset Pricing](Empirical AP/00-MOC_EF8083_Empirical_Asset_Pricing.md)
-- [Theoretical Asset Pricing](Theoretical AP/01_Single_Period_Models.md)
+- [Empirical Asset Pricing](Empirical%20AP/00-MOC_EF8083_Empirical_Asset_Pricing.md)
+- [Theoretical Asset Pricing](Theoretical%20AP/01_Single_Period_Models.md)
 
 The full navigation is in the book table of contents. Start from the track pages and follow the card links inside each note.