docs(viewer): clarify new locales ship via PR, not drop-in

Addresses CodeRabbit review on rohitg00#541.

Both README.md (Viewer language section + the env table at the bottom)
and .env.example referenced 'Drop src/viewer/locales/<lang>.json',
which is misleading for npm/global installs that ship dist/ without a
src/ tree. Rewords to explicitly call out the PR-against-repo path
(source checkout required) so users do not assume a runtime drop-in
mechanism exists.

Signed-off-by: Christian Walter <chris.walter@mail.de>

Author: ChristianWalterMedia

.env.example

@@ -104,7 +104,7 @@
 # -----------------------------------------------------------------------------
 
 # AGENTMEMORY_AUTO_COMPRESS=true                 # Run LLM compression on every observation batch (requires a provider key). Default off — synthetic compression handles most cases.
-# VIEWER_LANGUAGE=en                             # Viewer UI language. Built-in: en, de. Drop src/viewer/locales/<lang>.json to add more. Falls back to en for missing keys.
+# VIEWER_LANGUAGE=en                             # Viewer UI language. Built-in: en, de. Falls back to en for missing keys. New languages ship via PR (src/viewer/locales/<lang>.json) — see CONTRIBUTING.md.
 # AGENTMEMORY_INJECT_CONTEXT=true                # Inject recalled memories back into agent prompts (#143). Default off — hooks capture observations but do not modify conversation.
 # CONSOLIDATION_ENABLED=true                     # Run the 4-tier consolidation pipeline (memories → semantic → procedural). Default off — opt in once you've measured the LLM cost.
 # CONSOLIDATION_DECAY_DAYS=30                    # Age (days) after which non-reinforced memories decay during consolidation

README.md

@@ -925,7 +925,7 @@ The viewer UI defaults to English. Switch it via `.env`:
 VIEWER_LANGUAGE=de
 ```
 
-Restart agentmemory to apply. Built-in locales: `en`, `de`. Missing keys fall back to English. To contribute a new language, copy `src/viewer/locales/en.json`, translate the values, and open a PR — no code changes required. See [Contributing a translation](CONTRIBUTING.md#contributing-a-translation).
+Restart agentmemory to apply. Built-in locales: `en`, `de`. Missing keys fall back to English. New locales ship via PR against this repo — there is no drop-in location in packaged installs. To contribute, work from a source checkout: copy `src/viewer/locales/en.json` to `<lang>.json`, translate the values, and open a PR — no code changes required. See [Contributing a translation](CONTRIBUTING.md#contributing-a-translation).
 
 ---
 
@@ -1172,7 +1172,7 @@ Create `~/.agentmemory/.env`:
 # SNAPSHOT_ENABLED=false
 
 # Viewer language
-# VIEWER_LANGUAGE=en   # Viewer UI language. Built-in: en, de. Drop src/viewer/locales/<lang>.json to add more. Falls back to en for missing keys.
+# VIEWER_LANGUAGE=en   # Viewer UI language. Built-in: en, de. Falls back to en for missing keys. New languages via PR (src/viewer/locales/<lang>.json), see CONTRIBUTING.md.
 
 # Team
 # TEAM_ID=