feat(tui): standardize picker navigation keys (#22347)

## Why

Picker-style UI in the TUI has accumulated a mix of hardcoded navigation
keys. Some lists supported page movement, some did not; some accepted
Vim-like keys, while others only accepted arrows; and tabbed or
horizontally adjustable pickers had no shared keymap action for
left/right movement.

This PR makes picker/list navigation consistent and configurable so
users can rely on the same defaults across the TUI.

## What Changed

- Adds shared list keymap actions for:
  - vertical movement: `move_up`, `move_down`
  - horizontal movement: `move_left`, `move_right`
  - paging and jumps: `page_up`, `page_down`, `jump_top`, `jump_bottom`
- Adds defaults:
- Up/down: arrows, `Ctrl+P/N`, `Ctrl+K/J`, and plain `k/j` where text
input is not active
  - Page up/down: `PageUp/PageDown` and `Ctrl+B/F`
  - First/last: `Home/End`
  - Left/right: `Left/Right` and `Ctrl+H/L`
- Wires the shared list keymap through picker and list surfaces
including session resume, multi-select, tabbed selection lists,
settings-style lists, app-link selection, MCP elicitation,
request-user-input, and the OSS selection wizard.
- Keeps search behavior intact by reserving printable characters for
query text in searchable pickers.
- Updates keymap setup actions, config schema, snapshots, and focused
coverage for the new list actions.

## How to Test

1. Start Codex from this branch and open the session picker, for example
with an existing session history.
2. In the session list, verify that `Ctrl+J/K` moves the selection
down/up.
3. Verify that `Ctrl+F/B` pages down/up and `Home/End` jumps to the
first/last visible session.
4. Type printable search text such as `j` or `k` and confirm it updates
the query instead of navigating.
5. Focus a picker control that changes values horizontally, such as a
session picker toolbar control, and verify `Ctrl+H/L` changes the
focused value like left/right arrows.

Targeted tests run:

- `cargo test -p codex-tui keymap::tests::`
- `cargo test -p codex-tui keymap_setup::tests::`
- `cargo test -p codex-tui horizontal_list_keys`
- `cargo test -p codex-tui page_and_jump_navigation_use_list_keymap`
- `cargo test -p codex-tui ctrl_h_l_move_provider_selection`
- `cargo test -p codex-tui scroll_state::tests`
- `cargo test -p codex-tui
switching_tabs_changes_visible_items_and_clears_search`
- `cargo test -p codex-tui toggle_sort_key_reloads_with_new_sort`

Also ran `just write-config-schema`, `just fmt`, `just fix -p
codex-tui`, `just argument-comment-lint`, and `git diff --check`.

Note: `cargo test -p codex-tui` was attempted and still aborts in the
pre-existing
`tests::fork_last_filters_latest_session_by_cwd_unless_show_all` stack
overflow, which is unrelated to this branch.

codex-rs/core/config.schema.json

@@ -2606,8 +2606,14 @@
             "list": {
               "accept": null,
               "cancel": null,
+              "jump_bottom": null,
+              "jump_top": null,
               "move_down": null,
-              "move_up": null
+              "move_left": null,
+              "move_right": null,
+              "move_up": null,
+              "page_down": null,
+              "page_up": null
             },
             "pager": {
               "close": null,
@@ -3252,8 +3258,14 @@
           "default": {
             "accept": null,
             "cancel": null,
+            "jump_bottom": null,
+            "jump_top": null,
             "move_down": null,
-            "move_up": null
+            "move_left": null,
+            "move_right": null,
+            "move_up": null,
+            "page_down": null,
+            "page_up": null
           }
         },
         "pager": {
@@ -3350,6 +3362,22 @@
           ],
           "description": "Cancel and close selection view."
         },
+        "jump_bottom": {
+          "allOf": [
+            {
+              "$ref": "#/definitions/KeybindingsSpec"
+            }
+          ],
+          "description": "Jump to the last list item."
+        },
+        "jump_top": {
+          "allOf": [
+            {
+              "$ref": "#/definitions/KeybindingsSpec"
+            }
+          ],
+          "description": "Jump to the first list item."
+        },
         "move_down": {
           "allOf": [
             {
@@ -3358,6 +3386,22 @@
           ],
           "description": "Move list selection down."
         },
+        "move_left": {
+          "allOf": [
+            {
+              "$ref": "#/definitions/KeybindingsSpec"
+            }
+          ],
+          "description": "Move horizontally left in list pickers that support horizontal actions."
+        },
+        "move_right": {
+          "allOf": [
+            {
+              "$ref": "#/definitions/KeybindingsSpec"
+            }
+          ],
+          "description": "Move horizontally right in list pickers that support horizontal actions."
+        },
         "move_up": {
           "allOf": [
             {
@@ -3365,6 +3409,22 @@
             }
           ],
           "description": "Move list selection up."
+        },
+        "page_down": {
+          "allOf": [
+            {
+              "$ref": "#/definitions/KeybindingsSpec"
+            }
+          ],
+          "description": "Move list selection down by one page."
+        },
+        "page_up": {
+          "allOf": [
+            {
+              "$ref": "#/definitions/KeybindingsSpec"
+            }
+          ],
+          "description": "Move list selection up by one page."
         }
       },
       "type": "object"