docs: full humanizer pass (Layer 1 + adversarial audit)

The earlier commit only removed em dashes. This runs the full checklist:
- README: drop the significance-inflation ('the piece none of the cloud
  versions have') for a plainer, higher-rhythm line.
- SECURITY: replace the → glyph (an AI typographic tell) with prose.
- CONTRIBUTING: cut the boilerplate 'Thanks for your interest' opener.

Left deliberately: the bold-label bullets in SECURITY's trust model
(genuine item labels, idiomatic for a security doc, not the tautological
antipattern), and the neutral register of SECURITY/CHANGELOG/CONTRIBUTING
(neutral is correct for policy/reference prose; injecting 'voice' there
would be wrong). Verified clean of em dashes, glyphs, curly quotes,
copula avoidance, AI vocabulary, and filler.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Signed-off-by: mstrathman <matthew.strathman@gmail.com>

Author: mstrathman

CONTRIBUTING.md

@@ -1,7 +1,7 @@
 # Contributing to sqlite-predict
 
-Thanks for your interest. This project is pre-alpha; the API and formats
-are unstable, so it's a good time to influence them.
+This project is pre-alpha. The API and the on-disk formats are still
+unstable, which makes now a good time to influence them.
 
 ## Ground rules
 

README.md

@@ -29,9 +29,9 @@ the same shape to the database that runs everywhere else: on the edge, in
 the browser, on a phone, and inside the local-first databases that AI
 agents increasingly sit on.
 
-It also adds the piece none of the cloud versions have. Every prediction
-carries a **receipt**, so an agent can cite a number as a fact and an
-auditor can reproduce it.
+The cloud versions stop at the prediction. This one keeps going: every
+result carries a **receipt** that pins down the model and the exact data it
+read, so an agent can cite the number and an auditor can reproduce it.
 
 ## Operations
 

SECURITY.md

@@ -6,7 +6,7 @@ Please report suspected vulnerabilities privately. **Do not open a public
 issue for security reports.**
 
 - Use GitHub's [private vulnerability reporting][ghsa] on this repository
-  ("Security" tab → "Report a vulnerability"), or
+  (the Security tab, then "Report a vulnerability"), or
 - Email the Pure Storage security team at **psirt@purestorage.com**.
 
 Please include a description, reproduction steps or a proof of concept, and