feat(branding): own the psmux status-left and sweep pre-rename "md" leftovers

[AminDhouib]

Why

Every magent window advertised md in the left corner of its psmux status bar — the last loud piece of pre-rename branding a user actually looks at all day. That text was never magent's: it came from a personal ~/.tmux.conf (status-left '#[bold,fg=#a6e3a1] md #[default]' + status-left-length 5), which psmux loads at server start. A personal file can't be the product's branding, and it isn't editable from here.

magent has owned per-session status-bar decoration since v3.4.0, so the brand goes through the same door the F1/F2 hints already use.

What

1. Product-owned status-left. psmux.decoration_argv gains two argvs:

set -g status-left '#[bold,fg=green] magent #[default]'
set -g status-left-length 10

The length is load-bearing, not decoration: the personal conf sets status-left-length 5, which truncates magent to magen. Setting the brand without the length ships a visibly broken word. Verified live on a throwaway -L mgszbrand socket (created, status-left-length 5 set first to simulate the personal conf, then the two decoration commands; show -g reported 10 and the full brand string; server killed afterward). The user's live sessions and ~/.tmux.conf were not touched.

Both ride the single decoration_argv list, so the creation batch (platform/windows.py), up interactive, up --json, and attach pick them up with zero call-site changes — pinned by a new test_created_session_is_branded in test_platform_contract.py (the creation batch, which is the call site furthest from decorate_session).

2. Repo-wide user-visible "md" sweep. The mobile upload PWA was still branded "md upload" end to end — the rename had reached the manifest name ("magent upload") but nothing else.

Sweep inventory

Renamed (user-visible branding)

Where	Was	Now
psmux status bar, every session	md (from personal tmux.conf)	magent (product-owned)
upload page <title>	md upload	magent upload
upload page logotype <h1>	MD	magent
apple-mobile-web-app-title	md upload	magent upload
manifest short_name	md upload	magent
install-banner copy	Install <b>md upload</b>…	Install <b>magent upload</b>…
iOS Web Clip Label / PayloadDisplayName / PayloadDescription (x5)	md upload	magent upload
downloaded profile filename	md-upload.mobileconfig	magent-upload.mobileconfig
localStorage key	md-install-hide	magent-install-hide
service-worker cache key	md-v1	magent-v1
attention.md_windows_by_name	md_ prefix	magent_windows_by_name
cli/watch.py docstring	"md-grammar match"	"magent-grammar match"
scripts/lint_rules.py::_starts_md	_md suffix	_starts_title_prefix
README psmux section	hints only	documents the brand + the tmux.conf-override property

Two follow-ons the renames forced, both deliberate:

• SW cache cleanup. Renaming C would orphan the old md-v1 cache on already-installed clients, so activate now deletes every cache but the current one (standard PWA boilerplate; also makes any future version bump self-clean). Failure-swallowed like the rest of the SW.
• md-install-hide → magent-install-hide resets the "I dismissed the install banner" flag once per existing mobile client. One extra dismissible banner; judged worth it over leaving dead branding in shipped storage.

Deliberately left

Left alone	Why
MDTEST_* env vars (MDTEST_SSH_*, MDTEST_BROWSER, MDTEST_SOAK, MDTEST_MONITOR_LAB, MDTEST_INTERACTION, MDTEST_WT_COLD, MDTEST_TAILSCALE, MDTEST_ALLOW_REAL_HOME)	Test-tier gate contract, documented as such in CLAUDE.md. Renaming means touching workflow YAML + every gate site for zero user-visible benefit.
mdssh CI alias	Same — provisioned by .github/actions/setup-ssh-server into the runner's real ~/.ssh/config.
MD001–MD005 custom lint rule IDs	Rule-ID interface contract (MD002_ALLOW / md003_allowed allow-list keys, gate output, CLAUDE.md). Only the private helper _starts_md was renamed.
Test fixture name prefixes (mdrl-, mddist-, mdml-, mdhk, mdatt, mdssh*, mdtailnet, mddr-)	Throwaway unique-per-run session/window names inside CI tiers; never rendered to a user. Pure churn.
Local md = home / ".magent" path variables in e2e tests	Local variable names in test bodies; not branding.
.md file extensions, DESIGN.md / CLAUDE.md / E6.md / E9.md doc references	Obviously not branding.
platform/macos.py's mdfind	The actual macOS Spotlight binary.
CHANGELOG.md, pyproject.toml	Out of scope per brief.

The sweep introduces no occurrence of the pre-rename product name anywhere; the only surviving mention in the repo remains the CHANGELOG 2.0.0 rename line, as required.

Tests

• test_psmux.py::TestDecorateSession — the existing argv-shape pins were extended deliberately: two new exact-argv pins (status-left, status-left-length), a magent-survives-a-restyle pin mirroring the existing F1/F2 one, a _STATUS_BRAND_LEN >= len(" magent ") relationship pin (so the number can't drift away from the text it protects), and the swallow-the-exception test's count moved 2 → 4.
• test_platform_contract.py::test_created_session_is_branded — new; proves the creation batch inherits the brand with no call-site change.
• test_upload_browser.py — the three real-Chromium to_have_title assertions updated in the same commit (CI-only browser tier).

Gate

uv run python scripts/check.py — GATE PASSED (FULL), exit 0. 949 passed, 2 skipped, coverage 76.03% (floor 52%).