Relicense panll source-file SPDX headers AGPL→MPL-2.0 + reconcile PMPL drift #78

Follow-up to #75 / #77 (metadata relicense). The repo-licence declarations (LICENSE + toml/json) are converted to MPL-2.0 in #77. This issue tracks the source-file headers and PMPL drift, which were held back because they're not trivial.

AGPL-3.0-or-later SPDX headers to convert → MPL-2.0 (18 files)

src/ui/tea/:

• src/ui/tea/panll_gui.affine
• src/ui/tea/panll_tea.js

migration/ (16):

• migration/modules/{CloudGuard,Farm,LanguageForge,MassPanic,PanicAttack,Plaza,ServiceEndpoints,SpecBrowser,TangleViz,Tsdm,VerificationDashboard}Module.affine
• migration/modules/STATUS.md
• migration/msg/{Feedback,Orbital,VideoCoordination}Msg.affine

PMPL drift to reconcile → MPL-2.0

• .claude/CLAUDE.md (header # SPDX-License-Identifier: PMPL-1.0-or-later + "## License: PMPL-1.0-or-later on all original source files")
• tools/pcc/Cargo.toml (header comment line 1 = PMPL)
• .machine_readable/6a2/AGENTIC.a2ml and panel-clades/.machine_readable/6a2/AGENTIC.a2ml ("use PMPL-1.0-or-later")

Why this isn't trivial / blockers to handle

1. Pre-commit hook (.git/hooks/pre-commit) requires, for OWNED repos, that every staged file with extension zig|ex|idr|eph|py|js|ts|rs|c|h|adoc|md contain BOTH SPDX-License-Identifier: MPL-2.0 AND the owner string Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>. So STATUS.md and panll_tea.js will need owner-attribution lines added — decide the canonical header format first.
2. .affine files are not hook-checked but should still be made consistent.
3. .claude/CLAUDE.md is under a standing "do-not-touch in sweeps / ask-first" directive — needs explicit owner sign-off before editing.
4. Determine migration/'s status — is it active original source (→ MPL) or transitional/vendored content? Confirm before sweeping.
5. Leave functional AGPL references alone (the AttributionLicenseEngine/PlazaEngine code and deny.toml lists that analyse licence strings, and the anti-AGPL policy text in panel-clades).

Do as a manual, file-by-file, owner-reviewed change (no bulk auto-sweep), per estate licence policy.