feat(timeline): record a change by hand from the Timeline, a host's page or MCP log_change (#6350)

A change Steward can't see happen (a config edited, a disk swapped) is
recorded by whoever made it: what was done, its area, when (in the reader's
own zone), the hosts, what it was done to and a detail. Its author or an
admin edits or deletes it; recording, editing and deleting are audited and
those audit rows stay off the timeline. log_change records one as
"<user> via MCP", editable by the token's user.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

steward/templates/timeline/_entry.html

@@ -1,16 +1,19 @@
 {# One timeline entry's parts, shared by the Timeline page and a host's card.
    `item` is a timeline.service.view() row. #}
 
-{# What happened: its kind, the sentence, a note, and the full record while it is kept. #}
-{% macro entry_what(item) -%}
+{# What happened: its kind, the sentence, a note, and the full record while it
+   is kept; a change the reader recorded (or any, for an admin) can be edited,
+   returning to `back`. #}
+{% macro entry_what(item, back="/timeline/") -%}
 {%- set e = item.entry -%}
 <div>
   {%- if item.kind_label %}<span class="tone-dim">{{ item.kind_label }} · </span>{% endif -%}
   {{ e.summary }}
 </div>
-{%- if item.note %}<div class="field-hint">{{ item.note }}</div>{% endif %}
+{%- if item.note %}<div class="field-hint" style="white-space:pre-line;">{{ item.note }}</div>{% endif %}
 {%- if item.url %}<div class="field-hint"><a href="{{ item.url }}">Details</a></div>
 {%- elif item.gone %}<div class="field-hint">Details no longer kept</div>{% endif %}
+{%- if item.editable %}<div class="field-hint"><a href="/timeline/changes/{{ e.id }}/edit?back={{ back|urlencode }}">Edit</a></div>{% endif %}
 {%- endmacro %}
 
 {# Where: the hosts it happened on, each linked to its timeline, and what it happened to. #}