chore(helm): bump pipelock to 2.5.0 and surface 2.5 config (#1913)

* chore(helm): bump pipelock to 2.5.0 and surface 2.5 config

Bumps pipelock.image.tag from 2.2.0 to 2.5.0 and exposes the most
relevant 2.5 features as structured Helm values:

- pipelock.requestBodyScanning: scan outbound bodies and sensitive
  headers for prompt-injection and DLP payloads. Disabled by default;
  roll out with action=warn before flipping to block.
- pipelock.healthWatchdog: structured config for the wedge-detection
  watchdog with an exposeSubsystems toggle for /health detail.
- pipelock.mcpToolPolicy.rules: structured values for rendering
  mcp_tool_policy.rules including redirect-profile references.

Also fixes a latent config-validation regression: pipelock 2.x rejects
an enabled mcp_tool_policy with no rules, but the chart previously
defaulted to enabled=true with an empty rules list, which hard-fails
'pipelock check'. The default is now enabled=false; operators must
explicitly enable and provide at least one rule.

Refreshes README, CHANGELOG, docs/hosting/pipelock.md, docs/hosting/ai.md,
compose example pin comment, and pipelock.example.yaml to call out 2.5
highlights (Audit Packet v0 verifiers, SPIFFE-strict envelopes, scanner
attribution on MCP block receipts, pipelock doctor). Also fixes a stale
docs/hosting/mcp.md reference to the removed compose.example.pipelock.yml.

* chore(helm): fail helm template when mcp_tool_policy enabled with no rules

Adds a guard in asserts.tpl so an operator who sets
pipelock.mcpToolPolicy.enabled=true without populating
pipelock.mcpToolPolicy.rules gets a clear render-time error instead
of a container crash-loop with the pipelock validation message.

Per CodeRabbit feedback on #1913.

* Versions

---------

Co-authored-by: Juan José Mata <jjmata@jjmata.com>

compose.example.ai.yml

@@ -112,7 +112,7 @@ x-rails-env: &rails_env
 
 services:
   pipelock:
-    image: ghcr.io/luckypipewrench/pipelock:latest  # pin to a specific version (e.g., :2.2.0) for production
+    image: ghcr.io/luckypipewrench/pipelock:latest  # pin to a specific version (e.g., :2.5.0) for production
     container_name: pipelock
     hostname: pipelock
     restart: unless-stopped