feat(statusline): add opt-in context_position config for narrow terminals (#2937)

Extract composeStatusline() helper from duplicated inline template logic in
runStatusline() and renderStatusline(). Both call sites now route through the
helper, which accepts a position param ('end' | 'front', default 'end').

- 'end' (default) preserves byte-identical output to v1.38.x and earlier
- 'front' renders ctx immediately after model name, before the first │
- Invalid values silently coerce to 'end' at runtime (belt-and-suspenders;
  config-set rejects invalid values upfront via enum validator)

Adds statusline.context_position to VALID_CONFIG_KEYS in both CJS and TS
schemas, enum validator in config.cjs, docs row in CONFIGURATION.md,
and a changeset. Closes #2937.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/enh-2937-statusline-context-position.test.cjs

@@ -0,0 +1,121 @@
+'use strict';
+
+/**
+ * Enhancement #2937 — statusline opt-in `context_position` config.
+ *
+ * Asserts that:
+ *   - VALID_CONFIG_KEYS registers statusline.context_position (parity guard)
+ *   - Default (no config) renders ctx at tail — "end" layout
+ *   - Explicit "end" is byte-identical to default (regression guard)
+ *   - Explicit "front" puts ctx after model, before first " │ "
+ *   - Empty ctx with "front" leaves no stray separator
+ *   - Invalid value (e.g. "middle") silently falls back to "end" at runtime
+ *   - gsdUpdate warning stays leftmost in both "front" and "end" modes
+ */
+
+const { test } = require('node:test');
+const assert = require('node:assert/strict');
+
+const { composeStatusline } = require('../hooks/gsd-statusline.js');
+const { VALID_CONFIG_KEYS } = require('../get-shit-done/bin/lib/config-schema.cjs');
+
+// ── Parity guard ─────────────────────────────────────────────────────────────
+
+test('config schema registers statusline.context_position', () => {
+  assert.ok(
+    VALID_CONFIG_KEYS.has('statusline.context_position'),
+    'statusline.context_position must be in VALID_CONFIG_KEYS',
+  );
+});
+
+// ── Default / "end" layout ───────────────────────────────────────────────────
+
+test('default (no position arg) renders ctx at tail — end layout', () => {
+  const ctx = ' \x1b[32m████░░░░░░ 40%\x1b[0m';
+  const out = composeStatusline({ model: 'Claude', dirname: 'myproject', ctx });
+  // ctx should appear after dirname, not before first │
+  const dirIdx = out.indexOf('myproject');
+  const ctxIdx = out.indexOf(ctx);
+  assert.ok(ctxIdx > dirIdx, `ctx should be after dirname; got: ${out}`);
+});
+
+test('explicit "end" is byte-identical to default', () => {
+  const ctx = ' \x1b[32m████░░░░░░ 40%\x1b[0m';
+  const args = { model: 'Claude', dirname: 'myproject', ctx };
+  const defaultOut = composeStatusline(args);
+  const endOut = composeStatusline({ ...args, position: 'end' });
+  assert.strictEqual(endOut, defaultOut, 'explicit "end" must equal default output');
+});
+
+test('"end" with middle segment places ctx after dirname', () => {
+  const ctx = ' \x1b[32m████░░░░░░ 40%\x1b[0m';
+  const out = composeStatusline({ model: 'Claude', ctx, middle: 'doing work', dirname: 'proj', position: 'end' });
+  const dirIdx = out.indexOf('proj');
+  const ctxIdx = out.indexOf(ctx);
+  assert.ok(ctxIdx > dirIdx, `ctx should be after dirname in end mode; got: ${out}`);
+});
+
+// ── "front" layout ───────────────────────────────────────────────────────────
+
+test('"front" puts ctx after model name, before first │', () => {
+  const ctx = ' \x1b[32m████░░░░░░ 40%\x1b[0m';
+  const out = composeStatusline({ model: 'Claude', dirname: 'myproject', ctx, position: 'front' });
+  const firstPipe = out.indexOf(' │ ');
+  const ctxIdx = out.indexOf(ctx);
+  assert.ok(ctxIdx !== -1, `ctx should appear in output; got: ${out}`);
+  assert.ok(ctxIdx < firstPipe, `ctx should come before first │ in front mode; got: ${out}`);
+});
+
+test('"front" with middle segment: ctx after model, before first │', () => {
+  const ctx = ' \x1b[32m████░░░░░░ 40%\x1b[0m';
+  const out = composeStatusline({ model: 'Claude', ctx, middle: 'doing work', dirname: 'proj', position: 'front' });
+  const firstPipe = out.indexOf(' │ ');
+  const ctxIdx = out.indexOf(ctx);
+  assert.ok(ctxIdx < firstPipe, `ctx must precede first │; got: ${out}`);
+});
+
+// ── Empty ctx ────────────────────────────────────────────────────────────────
+
+test('empty ctx + "front" renders no stray separator', () => {
+  const out = composeStatusline({ model: 'Claude', dirname: 'myproject', ctx: '', position: 'front' });
+  // Should not have double-separator or leading │
+  assert.ok(!out.includes(' │  │ '), `stray separator found; got: ${out}`);
+  // Should still contain the single separator between model area and dirname
+  assert.ok(out.includes(' │ '), `expected at least one separator; got: ${out}`);
+});
+
+test('empty ctx + "end" renders no stray separator', () => {
+  const out = composeStatusline({ model: 'Claude', dirname: 'myproject', ctx: '', position: 'end' });
+  assert.ok(!out.includes(' │  │ '), `stray separator found; got: ${out}`);
+});
+
+// ── Invalid value fallback ───────────────────────────────────────────────────
+
+test('invalid position value silently falls back to "end" layout', () => {
+  const ctx = ' \x1b[32m████░░░░░░ 40%\x1b[0m';
+  const invalid = composeStatusline({ model: 'Claude', dirname: 'myproject', ctx, position: 'middle' });
+  const end = composeStatusline({ model: 'Claude', dirname: 'myproject', ctx, position: 'end' });
+  assert.strictEqual(invalid, end, `invalid position should produce same output as "end"; got: ${invalid}`);
+});
+
+test('invalid position "banana" silently falls back to "end"', () => {
+  const ctx = ' \x1b[33m██████░░░░ 60%\x1b[0m';
+  const invalid = composeStatusline({ model: 'Claude', dirname: 'proj', ctx, position: 'banana' });
+  const end = composeStatusline({ model: 'Claude', dirname: 'proj', ctx, position: 'end' });
+  assert.strictEqual(invalid, end, `invalid "banana" should fall back to "end"; got: ${invalid}`);
+});
+
+// ── gsdUpdate leftmost invariant ─────────────────────────────────────────────
+
+test('gsdUpdate warning is leftmost in "end" mode', () => {
+  const gsdUpdate = '\x1b[33m⬆ /gsd:update\x1b[0m │ ';
+  const out = composeStatusline({ gsdUpdate, model: 'Claude', dirname: 'proj', position: 'end' });
+  assert.ok(out.startsWith(gsdUpdate), `gsdUpdate should be leftmost in end mode; got: ${out}`);
+});
+
+test('gsdUpdate warning is leftmost in "front" mode', () => {
+  const gsdUpdate = '\x1b[33m⬆ /gsd:update\x1b[0m │ ';
+  const ctx = ' \x1b[32m████░░░░░░ 40%\x1b[0m';
+  const out = composeStatusline({ gsdUpdate, model: 'Claude', dirname: 'proj', ctx, position: 'front' });
+  assert.ok(out.startsWith(gsdUpdate), `gsdUpdate should be leftmost in front mode; got: ${out}`);
+});