ci: use vLLM 0.29 release image and align installation docs

Drop the old-base wheel reinstall and dependency repair block. Update source installation and configuration references to vLLM 0.29 while retaining explicitly matched 0.28 prebuilt Omni examples until its next release.

Validation: official image and CUDA/ROCm release artifacts checked; 6 documentation tests passed; diff whitespace checks passed. Markdown lint reports existing snippet/anchor issues. Container build not run: no builder available.
Signed-off-by: tzhouam <tzhouam@connect.ust.hk>

docs/getting_started/installation/README.md

@@ -1,7 +1,7 @@
 # Installation
 
 !!! important
-    vLLM-Omni is released against the matching upstream vLLM major/minor version. vLLM-Omni 0.28.x requires vLLM 0.28.x; the stable v0.28.0 instructions pin vLLM 0.28.0.
+    vLLM-Omni is released against the matching upstream vLLM major/minor version. The 0.29 development line requires vLLM 0.29.x; the source-install instructions pin vLLM 0.29.0. Published vLLM-Omni 0.28.0 wheels and images still require vLLM 0.28.x.
 
 vLLM-Omni supports the following hardware platforms: