chore: tidy #98 follow-ups (Pi import alias + test description)

Post-merge cleanup of PR #98:
- Pi's strip-tag-prefix.ts and temporal-awareness-pi.ts imported the shared
  tag-content-primitives via a raw cross-package path
  (../../plugin/src/...). Switch to the `@magic-context/core/...` workspace
  alias used everywhere else in Pi (the only two ../../plugin/src imports in
  the package).
- Fix a garbled test description: "transform ? ? notation only" → the intended
  "transform §N§ notation only" (the § chars were mangled on the way in).

No behavior change. Plugin 1796/0, Pi 403/0, tsc + biome clean.

Co-authored-by: Alfonso [Magic Context] <288211368+alfonso-magic-context@users.noreply.github.com>

Author: ualtinok

packages/pi-plugin/src/strip-tag-prefix.ts

@@ -12,7 +12,7 @@
  * Only `assistant` messages are stripped. User/tool messages keep intentional tags.
  */
 
-import { stripPersistedAssistantText } from "../../plugin/src/hooks/magic-context/tag-content-primitives";
+import { stripPersistedAssistantText } from "@magic-context/core/hooks/magic-context/tag-content-primitives";
 
 /**
  * Mutate the given assistant message's text parts in place to strip MC tag notation.

packages/pi-plugin/src/temporal-awareness-pi.ts

@@ -23,14 +23,14 @@
  * every pass (intentional — same as OpenCode, see transform.ts:648).
  */
 
+import {
+	peelLeadingMcTagNotation,
+	stripTagPrefix,
+} from "@magic-context/core/hooks/magic-context/tag-content-primitives";
 import {
 	TEMPORAL_MARKER_PATTERN,
 	temporalMarkerPrefix,
 } from "@magic-context/core/hooks/magic-context/temporal-awareness";
-import {
-	peelLeadingMcTagNotation,
-	stripTagPrefix,
-} from "../../plugin/src/hooks/magic-context/tag-content-primitives";
 
 type PiTextContent = { type: "text"; text: string; textSignature?: string };
 type PiImageContent = { type: "image"; data: string; mimeType: string };

packages/plugin/src/hooks/magic-context/tag-content-primitives.test.ts

@@ -15,7 +15,7 @@ const SECTION = "\u00a7";
 
 const DEGREE = "\u00b0";
 
-describe("stripTagPrefix (transform ? ? notation only)", () => {
+describe("stripTagPrefix (transform §N§ notation only)", () => {
     it("#given well-formed leading prefix #when stripTagPrefix runs #then removes it", () => {
         expect(stripTagPrefix(`${SECTION}42${SECTION} Hello`)).toBe("Hello");
     });