docs: add 0.6.0 changelog entries

[utiberious]

Adds changelog entries for all PRs merged since 0.6.0-dev began (after 0.5.2), grouped by theme. Does not include the :release: marker or version bump — those will come in a separate PR once remaining 0.6.0 PRs land.

New features

• feat(ga): add Cl(p,q,r) kingdon-like interface for Clifford algebras #550 Cl(p,q,r) kingdon-compatible interface (closes Provide a kingdon-like interface, and run cross-library test cases #524)
• feat(mv): add __rtruediv__ to support scalar/Mv expressions #543 Mv.__rtruediv__ for scalar/Mv (closes expression like 1/<Mv> raise exception #512)
• Add shirokov_inverse and hitzer_inverse #530 shirokov_inverse, hitzer_inverse

Bug fixes

• fix(interop): reset dual mode to galgebra default in interop.Cl #556 interop dual mode contamination (closes interop.Cl dual mode interaction: session contamination and per-instance fix #555)
• fix(mv): wrap norm() in Abs for even-grade multivectors #554 norm() wrapped in Abs (closes norm has no abs bar for even grades #522)
• fix(mv): improve is_versor() per GSG's analysis #536 is_versor() improvement (closes .is_versor() method in class Mv of module mv.py uses an incorrect algorithm #533)

Examples and docs

• feat(examples): add sundial problem demonstrating core GA operations #549 + feat(examples): validate galgebra against Goyder cheat sheet (#506) #557 sundial example + cheatsheet tests (closes The sundial problem and a cheat sheet by Russell Goyder #506)
• docs(examples): add tutorial for extracting coordinates from multivectors #551 coordinates tutorial
• docs: improve documentation of available GA operations in README #548 README operations docs (closes Improve doc on available GA operations in README #523)

Tests and maintenance

• test(lt): add regression tests for lt.matrix() on oblique/non-Euclidean metrics (#461) #558 lt.matrix() regression tests (closes actions of generic linear transformations; matrices of linear transformations #461)
• test(printer): add regression test for extra \\cdot in LaTeX output #545 extra \cdot regression test
• refactor(ga): simplify er_blade to delegate to Mul #552 + refactor(ga): simplify ReciprocalFrame with clearer loop structure #553 er_blade and ReciprocalFrame refactors
• Fix CI #535 CI fix

[utensil]

CI all green, content is correct, organization is good.

One style note: the existing changelog uses the linked issue number as the primary identifier (e.g. :bug:533`` for the bug that was fixed). Using the PR number as primary is reasonable — PRs carry more context than old issues — but it's inconsistent with existing entries.

Since the entry already starts with e.g. :bug:536`` (which links to the PR), just ending with something like "Closes :issue:533" or "Fixes :issue:`533`" is enough to cover both — the PR link is at the front, the issue link is at the end.