docs: bring the changelog and user guide up to date for the release

[mcdope]

Release prep. The changelog had drifted in two directions at once, and three user-guide pages had claims the code no longer backs.

1. Six player-visible changes were missing

Cross-checked the 41 commits touching src/ since beta-6 against the Unreleased section:

• the first-run guided tour
• opening a repository on its least complex file instead of its most complex one
• the cap on locked doorways per level
• in-room teleporters becoming an exception rather than the rule
• the C# interface parse fix, which had made those repos generate unfinishable levels
• TODO encounters following their own text

2. Dev entries had taken over

51% of the Unreleased section was Dev: — more than half of a player-facing document, including its two longest entries. README.md:195 and both adding-a-*.md guides state the rule: player-visible changes, in player-facing voice.

The drift is measurable:

section	entries	dev share
beta-1 – beta-3	20	0%
beta-4	23	8%
beta-5	14	7%
beta-6	35	42%
Unreleased (before)	27	51%
Unreleased (after)	24	20%

Condensed 14 dev entries into 5 short ones grouped at the end — the detail already lives in doc/dev/history.md, so nothing is lost — and ordered the section New → Changed → Fixed. Every original player-facing entry is preserved verbatim (checked programmatically: 0 dropped, 0 duplicated, all 7 sections intact).

3. User docs, checked against the code rather than the commit messages

• getting-started.md claimed the game opens a workspace on "the highest-complexity file". That's the exact behaviour that got fixed, and it contradicted README.md, which already said least-complex. Also now documents the guided tour, which nothing outside tips.md mentioned.
• hud-and-ui.md still described Keys as a held/total count. The HUD draws one coloured pip per locked room now — hud.ts's own comment explains why the count was dropped ("it degrades into collected / collectable, a completionist stat wearing a resource's clothes"). Adds the cheated-run badge, the Player name setting, and the leaderboard's Player column and bot-profile labels.
• level-design.md promised a locked room for every private method and a teleporter for every goto pair. Both are capped now, so both promises overstated the generator.

mechanics.md needed nothing — already current on the flamethrower falloff and on Elites being packs. Worth saying, since "audit the docs" tends to produce edits whether or not they're warranted.

Verification

2,927 src tests, tsc --noEmit clean, no broken relative links in any touched file. No code changed.