Feat v0.6.12 extension css isolation

Prefix enforcement prevents extension CSS from leaking into the kernel
or sibling extensions. All 12 in-tree packages migrated to .ext-{slug}-*
naming convention.

- Add data-ext attribute to extension mount container
- Add CSS linter (scripts/lint-package-css.sh) enforcing .ext-{slug} prefix
- Add kernel CSS contract doc (docs/EXTENSION-CSS.md)
- Migrate 12 packages: chat, dashboard, editor, git-board, hello-dashboard,
  icd-test-runner, notes, schedules, sdk-test-runner, tasks,
  team-activity-log, workflow-demo (CSS + JS in lockstep)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/team-activity-log/css/main.css

@@ -2,7 +2,7 @@
  * Uses platform CSS variables exclusively for theming.
  */
 
-.tal-shell {
+.ext-team-activity-log-shell {
   max-width: 720px;
   margin: 0 auto;
   padding: 24px 16px;
@@ -14,34 +14,34 @@
 
 /* ── Header ────────────────────────────────── */
 
-.tal-header {
+.ext-team-activity-log-header {
   display: flex;
   align-items: center;
   justify-content: space-between;
   gap: 12px;
 }
 
-.tal-header__left {
+.ext-team-activity-log-header__left {
   display: flex;
   align-items: baseline;
   gap: 10px;
 }
 
-.tal-title {
+.ext-team-activity-log-title {
   font-size: 20px;
   font-weight: 600;
   color: var(--text);
   margin: 0;
 }
 
-.tal-subtitle {
+.ext-team-activity-log-subtitle {
   font-size: 13px;
   color: var(--text-3);
 }
 
 /* ── Entry Form ────────────────────────────── */
 
-.tal-form {
+.ext-team-activity-log-form {
   display: flex;
   gap: 8px;
   background: var(--bg-surface);
@@ -50,7 +50,7 @@
   padding: 10px 12px;
 }
 
-.tal-form__select {
+.ext-team-activity-log-form__select {
   background: var(--bg-raised);
   border: 1px solid var(--border);
   border-radius: var(--radius);
@@ -61,7 +61,7 @@
   cursor: pointer;
 }
 
-.tal-form__input {
+.ext-team-activity-log-form__input {
   flex: 1;
   background: var(--bg-raised);
   border: 1px solid var(--border);
@@ -74,15 +74,15 @@
   transition: border-color var(--transition);
 }
 
-.tal-form__input:focus {
+.ext-team-activity-log-form__input:focus {
   border-color: var(--accent);
 }
 
-.tal-form__input::placeholder {
+.ext-team-activity-log-form__input::placeholder {
   color: var(--text-3);
 }
 
-.tal-form__btn {
+.ext-team-activity-log-form__btn {
   background: var(--accent);
   color: #fff;
   border: none;
@@ -95,25 +95,25 @@
   transition: background var(--transition);
 }
 
-.tal-form__btn:hover:not(:disabled) {
+.ext-team-activity-log-form__btn:hover:not(:disabled) {
   background: var(--accent-hover);
 }
 
-.tal-form__btn:disabled {
+.ext-team-activity-log-form__btn:disabled {
   opacity: 0.5;
   cursor: default;
 }
 
 /* ── Filters ───────────────────────────────── */
 
-.tal-filters {
+.ext-team-activity-log-filters {
   display: flex;
   align-items: center;
   gap: 6px;
   flex-wrap: wrap;
 }
 
-.tal-filter {
+.ext-team-activity-log-filter {
   background: var(--bg-raised);
   border: 1px solid var(--border);
   border-radius: var(--radius);
@@ -125,18 +125,18 @@
   transition: all var(--transition);
 }
 
-.tal-filter:hover {
+.ext-team-activity-log-filter:hover {
   background: var(--bg-hover);
   color: var(--text);
 }
 
-.tal-filter.active {
+.ext-team-activity-log-filter.ext-team-activity-log-active {
   background: var(--accent-dim);
   border-color: var(--accent);
   color: var(--accent);
 }
 
-.tal-count {
+.ext-team-activity-log-count {
   margin-left: auto;
   font-size: 12px;
   color: var(--text-3);
@@ -144,13 +144,13 @@
 
 /* ── Entry List ────────────────────────────── */
 
-.tal-entries {
+.ext-team-activity-log-entries {
   display: flex;
   flex-direction: column;
   gap: 6px;
 }
 
-.tal-entry {
+.ext-team-activity-log-entry {
   background: var(--bg-surface);
   border: 1px solid var(--border);
   border-radius: var(--radius);
@@ -158,36 +158,36 @@
   transition: border-color var(--transition);
 }
 
-.tal-entry:hover {
+.ext-team-activity-log-entry:hover {
   border-color: var(--border-light);
 }
 
-.tal-entry__header {
+.ext-team-activity-log-entry__header {
   display: flex;
   align-items: center;
   gap: 8px;
   margin-bottom: 4px;
 }
 
-.tal-entry__category {
+.ext-team-activity-log-entry__category {
   font-size: 11px;
   text-transform: uppercase;
   letter-spacing: 0.02em;
 }
 
-.tal-entry__user {
+.ext-team-activity-log-entry__user {
   font-size: 13px;
   font-weight: 500;
   color: var(--text);
 }
 
-.tal-entry__time {
+.ext-team-activity-log-entry__time {
   font-size: 12px;
   color: var(--text-3);
   margin-left: auto;
 }
 
-.tal-entry__delete {
+.ext-team-activity-log-entry__delete {
   background: none;
   border: none;
   color: var(--text-3);
@@ -199,15 +199,15 @@
   transition: all var(--transition);
 }
 
-.tal-entry:hover .tal-entry__delete {
+.ext-team-activity-log-entry:hover .ext-team-activity-log-entry__delete {
   opacity: 1;
 }
 
-.tal-entry__delete:hover {
+.ext-team-activity-log-entry__delete:hover {
   color: var(--danger);
 }
 
-.tal-entry__message {
+.ext-team-activity-log-entry__message {
   font-size: 14px;
   color: var(--text);
   line-height: 1.5;
@@ -215,8 +215,8 @@
 
 /* ── Empty / Loading ───────────────────────── */
 
-.tal-empty,
-.tal-loading {
+.ext-team-activity-log-empty,
+.ext-team-activity-log-loading {
   text-align: center;
   padding: 40px 16px;
   color: var(--text-3);