docs(reference): audit and fix 4 pages (typography, dup H1, Related)

docs/reference/api-usage-costs.md

@@ -3,12 +3,10 @@ summary: "Audit what can spend money, which keys are used, and how to view usage
 read_when:
   - You want to understand which features may call paid APIs
   - You need to audit keys, costs, and usage visibility
-  - You’re explaining /status or /usage cost reporting
+  - You're explaining /status or /usage cost reporting
 title: "API usage and costs"
 ---
 
-# API usage & costs
-
 This doc lists **features that can invoke API keys** and where their costs show up. It focuses on
 OpenClaw features that can generate provider usage or paid API calls.
 
@@ -154,7 +152,7 @@ See [Web tools](/tools/web).
 
 - `FIRECRAWL_API_KEY` or `plugins.entries.firecrawl.config.webFetch.apiKey`
 
-If Firecrawl isn’t configured, the tool falls back to direct fetch plus the bundled `web-readability` plugin (no paid API). Disable `plugins.entries.web-readability.enabled` to skip local Readability extraction.
+If Firecrawl isn't configured, the tool falls back to direct fetch plus the bundled `web-readability` plugin (no paid API). Disable `plugins.entries.web-readability.enabled` to skip local Readability extraction.
 
 See [Web tools](/tools/web).
 
@@ -193,7 +191,7 @@ See [Talk mode](/nodes/talk).
 ### 10) Skills (third-party APIs)
 
 Skills can store `apiKey` in `skills.entries.<name>.apiKey`. If a skill uses that key for external
-APIs, it can incur costs according to the skill’s provider.
+APIs, it can incur costs according to the skill's provider.
 
 See [Skills](/tools/skills).
 

docs/reference/application-modernization-plan.md

@@ -7,8 +7,6 @@ read_when:
   - Turning a broad product quality review into phased engineering work
 ---
 
-# Application modernization plan
-
 ## Goal
 
 Move the application toward a cleaner, faster, more maintainable product without

docs/reference/credits.md

@@ -5,8 +5,6 @@ read_when:
 title: "Credits"
 ---
 
-# Credits and Acknowledgments
-
 ## The name
 
 OpenClaw = CLAW + TARDIS, because every space lobster needs a time and space machine.

docs/reference/openclaw-sdk-api-design.md

@@ -379,7 +379,7 @@ Benefits:
 - low-level consumers still have full protocol access
 - high-level consumers get the small product API
 
-## Related docs
+## Related
 
 - [OpenClaw App SDK](/concepts/openclaw-sdk)
 - [Gateway RPC reference](/reference/rpc)