feat: begin Icod.DCurses 2.0 Terminal-only migration

[uniblab]

Summary

This PR is the active Icod.DCurses 2.0 migration branch. It preserves the published 1.6 line while moving all terminal-facing behavior toward the strict dependency direction DCurses -> Terminal -> TermInfo.

Completed checkpoints:

• T2001 accepted against published Icod.Terminal 1.18.0: dependency/API inventory, approved break manifest, 1.6 behavioral baseline, safe unknown-rendition recovery, transaction limits/stale-epoch/cost/cleanup witnesses.
• T2002 accepted: 2.0.0-alpha.1 package identity, 2.0.0.0 assembly identity, public profile/dimensions cutover, parity hardening, and a reviewed 2.0 development API baseline.
• Attribution, copyright, and license wording in the root README was corrected by the maintainer and is preserved.

T2002 public boundary

The approved 2.0 changes are:

• replace CursesSession.Terminal : Icod.TermInfo.TerminalDescription with CursesSession.Profile : Icod.Terminal.TerminalProfile;
• return TerminalControlResult<TerminalDimensions> from both dimension methods;
• expose CursesLifecycleEvent.Dimensions : TerminalDimensions?;
• advance AssemblyVersion from 1.0.0.0 to 2.0.0.0.

The development fingerprint is 75 exported types, 559 canonical contract lines, SHA-256 1d33658358af26049d858e084a80d9f3b80abab974c1c4d3bfb36c2c2b477c65. Exported type names are unchanged from 1.6, historical fingerprints remain immutable, and recursive public dependency checks find no TermInfo type.

Verification

Executable acceptance head: f030d1b1b7e18f4566c171d4fc8f5a4765a3f8cc.

Workflow 35390788950 passed all seven jobs:

• package candidate;
• Windows x64 and ARM64;
• Linux x64 and ARM64;
• macOS x64 and ARM64.

The Linux x64 job passed 912 tests on each of net8.0, net9.0, and net10.0, with zero failures and skips.

See docs/T2001-Terminal-Boundary-and-Readiness-Gate.md, docs/T2002-Public-Terminal-Cutover-Gate.md, and the 2.0 roadmap for exact evidence.

Remaining ordered work

T2003 is next: migrate presentation capability projection, color/attribute/glyph resolution, rendition transitions/baseline, ACS, cursor movement, and alerts through Terminal semantic screen APIs.

T2004-T2006 then migrate optimization and transactional refresh/recovery. T2007 removes the temporary direct Icod.TermInfo 1.15.0 reference and internal TerminalDescription seam and proves the final package boundary. TermInfo remains a legitimate transitive Terminal dependency.

No merge, tag, release, or NuGet publication is authorized by the current checkpoints.

[uniblab]

T2001 execution checkpoint:

• Froze the complete TermInfo/raw-output coupling inventory and approved 2.0 API-break manifest at 01ce230 (7/7 green).
• Published an intentional downstream Terminal 1.17.0 package witness at 269c76a. It failed exactly as intended on net8.0/net9.0/net10.0 with CS1061: TerminalScreenPlanner has no PlanRenditionBaseline() (RED run, representative job).
• Recorded the smallest owning-repository correction and blocked gate in docs/T2001-Terminal-Boundary-and-Readiness-Gate.md; updated both roadmaps.
• Removed the intentionally uncompilable witness and test-only package reference in a normal follow-up commit. No DCurses production, package dependency, version, or test-project change remains in the PR diff.
• Exact final head 21fe26954157e819320e9df92af6b388d4931473 is 7/7 green.

T2001 and T2002+ remain blocked pending separately authorized Terminal work. The proposed additive contract is TerminalScreenPlanner.PlanRenditionBaseline(), published in a new minor release (provisionally Icod.Terminal 1.18.0).