ai-stack: fix invalid YAML in generated docker-compose.yml healthchecks

Confirmed live: `docker compose pull` failed with "yaml: line 44, column
29: mapping values are not allowed in this context" during the "Starting
Stack" phase of local-ai-setup.sh. Root cause: two healthcheck blocks
(ollama, chromadb) crammed interval/timeout/retries onto one
semicolon-separated line —

    interval: 30s; timeout: 10s; retries: 5

— which isn't valid YAML; a scalar value can't contain a second `key:`
token like that unless quoted. Split each into three separate properly
indented keys, matching how every other multi-key block in this same file
is written.

Verified by generating the actual docker-compose.yml via the real heredoc
(same one docker-stack.md's variables would produce) and parsing the
result with PyYAML — line 44 is exactly the fixed `interval: 30s` line,
and the full file now parses as valid YAML.

Pre-existing bug in the vendored source, unrelated to this session's
earlier ai-stack.sh/local-ai-setup.sh changes (those only touched the
pull-models.sh heredoc and the cloud-provider prompt, both well before
this point in the install) — first surfaced now because this is the first
run in this session to actually reach the "Starting Stack" step rather
than stopping earlier.

vendor/ai-stack/local-ai-setup.sh

@@ -596,7 +596,9 @@ services:
               capabilities: [gpu]
     healthcheck:
       test: ["CMD","ollama","list"]
-      interval: 30s; timeout: 10s; retries: 5
+      interval: 30s
+      timeout: 10s
+      retries: 5
 
   open-webui:
     image: ghcr.io/open-webui/open-webui:main
@@ -630,7 +632,9 @@ services:
       - ANONYMIZED_TELEMETRY=FALSE
     healthcheck:
       test: ["CMD-SHELL","wget -qO- http://localhost:8000/api/v2/heartbeat || exit 1"]
-      interval: 15s; timeout: 5s; retries: 5
+      interval: 15s
+      timeout: 5s
+      retries: 5
 
   rag-server:
     image: python:3.11-slim